At least 50,000 Georgians have been protesting outside parliament in the capital, Tbilisi, urging President Mikhail Saakashvili to step down.
Opposition leaders urged the crowd to keep the protest going
The crowd also called for early parliamentary elections.
They accused Mr Saakashvili of heading a corrupt, authoritarian government and want him to be ousted democratically.
The government rejects the claims. It is Georgia's worst political crisis since the 2003 Rose Revolution that swept Mr Saakashvili to power.
Elections are not due until late 2008.
Poverty and discontent
Many protesters arrived in convoys from the provinces early on Friday.
As evening fell, an opposition leader, Levan Gachechiladze, told the crowd to remain in the square until their demands were met.
"We need to stay. We need only a few days before victory," the AFP news agency quoted him as saying.
The agency estimated that some 10,000 protesters had stayed on after nightfall.
The government has accused the opposition of using the protest as a form of blackmail.
The country's previously weak and divided opposition parties formed a united front last month, and began a nationwide protest campaign against the Georgian leader.
The BBC's Matthew Collin in Tbilisi says the opposition is also hoping to capitalise on discontent with widespread poverty in Georgia.
The country is still struggling to recover from years of post-Soviet economic decay, instability and civil war.
Call for concessions
"This government didn't keep any of the promises they made... People demand basic things - people are hungry," one protester told the BBC.
Mr Saakashvili says he has rescued Georgia's economy
Another protester, Omar Pirtskhelava, a 17-year-old tourism student, told the BBC News website thousands of people had streamed in from various regions of Georgia.
They has arrived chanting the slogans "We Are One Georgia", "Go Saakashvili" and "Viva Georgia".
Kakha Kukava, a Conservative Party lawmaker, denied the opposition was trying to stir up more social unrest.
"We are not calling people for a revolution, we are calling people for a protest," he said.
"We are demanding fair elections and we think that it's very important for Georgia just now to make the first precedent to replace the government on the basis of elections, not on the basis of revolution."
Many of President Saakashvili's policies remain popular, our correspondent says.
The staunchly pro-Western president said on Thursday that Georgia was a failed state before he came to power but had now become a model of democratic development and economic reform.
He has suggested minor changes to the electoral process to ensure more opposition representation in parliament - but the opposition says this is not enough.
I just came back from the demonstration. Why are people protesting? This is the question that is most commonly asked by the foreigners. The answer to this question is that Saakashvili has painted many houses, constructed roads, communications line and so on, but failed to deliver what people fought for during the Rose Revolution.
The entire society has become anti-Saakashvili, doctors, teachers, writers, students, pensioners, businessman and so on everyone is dissatisfied by Saakshvili?s rule and unjust policies, he has created the system, where judiciary is under 100% control of the state and by the General Prosecutor in particular. The law exists only for certain category of people...
Society is scared, everyone knows that in case of accused allegations from the state, the is no way one can find the truth, no one will be able to prove the truth in the court since it is completely dominated by the state. Businessman are terrorized on daily basis, state is trying to extort from them as much money as possible in order to create an illusion that the budget is overfilled due to the economic growth.
Business environment is very unfriendly. Large and most profitable businesses are entirely controlled by Saakashvili?s close associates and family and there is no way for outside player to enter the same business. Families with low incomes have huge dissatisfaction since no jobs were created for the majority of them and due to huge inflation these people barely make a living.
And after all of this, when about 100 thousand people go on to streets in order to make their demands more visible to Saakashvili, government?s and the ruling party?s response is that they will not accept ultimatums from anyone, and Saakashvili himself did not appear to people at all.
The question is asked, why is the West labelling Saakashvili as the ?Democratic Leader? of Georgia? Over the years, Saakashvili has transformed Georgia from semi-democratic to authoritarian state. Where is the democracy that he is talking so often about?
Russians are mistaken to think it's Saakashvili that is the problem in our relations, the real problem is Russia's suppot to separatists. Changing Saakashvili to someone else (unless it's Kremlin's puppet) won't change it.
I don't find massive protests a reasonable way to move election date just by about 6 month. If you don't like this government (and many do like it, despite problems, as there are tremendous improvements in Georgia in almost all areas) then just go and elect new one!
Remember that changes to the constitution, that postponed election date by about 6 month are already one year old! If they were so unacceptable, why nobody protested one year earlier???
Mikheil, Leverkusen, Germany
I'm glad that picture of united Georgia lead by Mr.Saakashvilli and policy american establishment artificial implemented there to confront Russia finally falling apart.I'v got a lot off friends of mine who georgian and I dont understand how this american propoganda project in Georgia could continue blaming their neighbour Russia for all possible sins with all population living in drastic povery.And you should remember that in Soviet time Georgia was one of the richest republic of Soviet Union.Now it's poverest in Europe.Try to feel yourself free if you can't feed your basic minimal needs.Mr.Saakashvilli it's time to go back to your american bosses
Andrey, Istanbul Turkey
I am an Argentine opening a business here in Tbilisi. I must admit that the facade of doing business in Georgia is attractive... but once you are in then many other things become apparent. Not quite what was advertised. Many Georgians agree that life here in Tbilisi is better than it was but Saakashvili's anti-Russian position has hurt trade and has resisted the economy from better growth.
About the opposition, I am not sure. If Saakashvili steps down and the united opposition front claims victory, it will be like cats in a bag on who will be leader. Plus will it change much? All here might even be worse...
Pedro, Tbilisi, Georgia
Nothing has changed since the Rose Revolution 2003... Most of people live in poverty. Have you seen any European country holding presidential and parliamentary elections simultaneously? So, it's up to you to judge "Georgian democracy"
Saakashvili has done only ONE positive thing - turned Georgia to the way which never leads back to the dependency on Russia. That is it. I think he has to leave ASAP.
I passionately desire that this country becomes truly independent. First of all it is because Gergians is one of not that many nations in the world which is truly independent in it's heart. Georgian soul is amasing and truly independent (I've got impression that this is a key feature of the national spirit). Unfortunately nowadays president was not fair with the nation when he claimed to fight for the real independence of Georgia. Being unfair in front of the spirit of the nation is a crime in front of the history of the nation and the nation itself.
This is the reason for Saakashvili to leave. This is a reason for Russian government to learn this lesson of the deep respect to this country and nation...
I think Mr.Saakashvili makes a big mistake not going to manifestation.He could just come and tell his people,that every problem they want to be solved will be done soon.On the other hand I dont understand why are this people dissatisfied because I live there and see that this country really makes progress the wages is almost doubled the pension too. I think that this protest is rolled up by the opposition to go in advance and people who went on this manifestation with themselfs are being trapped right now.
I am a person who lived in London for nearly 5 years and returned back to Georgia after the rose revolution only. What I have seen is that during all this time government has done the most and still continuing to reform the country to turn it into a civilized society.
It's obvious that reforms and particularly vast and brisk reforms can?t favor everyone. When people see that they don?t have problems with electricity, roads and infrastructure anymore, they got used to it and feel as if it had to be like that and require more.
Those who lost jobs (and some of them comfort) because of laziness, corruption or their incapability to meet new modern standards are naturally offended. And these pathetic opposition parties are using them (in some cases honest but uneducated peasants) to come to power having no idea about any macro or microeconomic trends and consequences.
In short, one need to see the faces of those power lusting, uneducated and pathetic leaders of the opposition parties and will get complete picture of what?s happening here.
David, Tbilisi, Georgia
I can not understand what the opposition wants. There no promises to the Georgian People from opposition. What they are looking for? God knows. The question is who are the opposition leaders? They are the people who could not get seats inside the government. They just look for more financial support then anything else. They just need more power to make more money. People are "dolls? there to play with.
I still think that government needs more time to do the job...
Zviad, London, UK
Pink, velvet, orange, call it whatever you want, revolutions are clearly orchestrated by west to impose their own interests, not to bring locals a better life. That itself may not necessarily be a bad thing, as we would all like to see more real democracy around the globe. This is assuming west is investing after they top up the previous regimes. However, the reality is rather different, once in power, pro-west politicians are using same mechanisms as their predecessors, everyday life improvement is associated with a few extra McDonalds on streets.
Playing the card of hope for better life can work once or twice, but constantly failing to deliver will actually backfire. It is great that we don?t have to go into the war for imposing our values, like in Iraq or Afghanistan, but we apparently fell short of the full package delivery to these people. If we are not prepared to go all the way, maybe we should even stay away to begin with.
I had so many hopes concerning our government after Rose revolution, Saakashvili with his team had a great opportunity to create more democratic Georgia, but they sowed terror in the country, they divided Georgia among "their supporters" and "Others". Our government is corrupted. Of course they made some success like breakdown of Aslan Abashidze's regime in Adjaria, development of our Army etc, but there is no democracy in our country, we don't have fair court and government doesn't respect human rights. Those are the main reason why are Georgian people protesting: we want democracy in our country.
As regards Russia and Mr Andreas Heltmann's comment concerning pro-American and pro-Russian politics, it's deeply unfair. While Russia supports separatism in Georgia, it's impossible for us - Georgian people to support pro-Russian policy. We protest against our government because they more and more resemble us Putin?s rule, we won?t let them a return of totalitarianism.
Natia, Tbilisi, Georgia
Although most of the claims posted here are at least slightly exaggerated, it is surely a good sign that the opposition could finally pull up its efforts and garner considerable popular support. It is a reality check for the government, which increasingly became detached from the public in the past two years.
It would be unfair to overlook the efforts made in institutional and economic reforms in the past four years. But the real problem is that almost nothing has been done to improve the social safety net - this once largely egalitarian society is visibly becoming segregated and marginalized.
Why socialism prevailed in this country so long was in part due to the fact that western capitalism has always been extremely unpopular. Any government which fails to acknowledge this popular dissent will face similar deadlock.
Alex Maisuradze, New York
From our (Russian) view it is not normal to turn Georgian people against us that live together for 100 years peacefully. I am sure USA or any other country don't care so much as Russia what happens to Georgia because we have border with them! Saakashvili must go because he is the only Georgian president who brought Russia and Georgia as close as it gets to the war!
Vladyslav, Rostov, Russia
Georgian people are fed up with the corrupt, cynical, terrorist government, torturing its nation for 4 years! I completely agree with those standing in front of the Parliament building in Tbilisi demanding their constitutional right to be respected and protected.
Nina Bestaeva, Tbilisi, Georgia
Saakashvili is a US puppet, but not just Americans, you Brits, were telling the world lies about Georgian democracy, it was authoritarian corruption with dissidents sent behind the bars, worse than Russia. Now, start telling the truth about this Orange Demolition.
I am a German working in Georgia. The protests, as far as I can tell, are peaceful. I get the feeling that most Georgians are fed up with the current government not only because of corruption, but more so because it's pro-American and anti-Russian.
Andreas Heltmann, German, living in Georgia
Yes, today all Georgia was affected by what is happening in the country. I was at the manifestation with my friends...
Unfortunately Mr Saakashvili and his government lost contact... with people, people who believed and voted for them three years ago. But most pre- and post-election promises stayed unrealised. I personally feel sad today, because really believed in Saakashvili, in his young and talented ministers, was proud and happy to have such a progressive government, hoped that finally we have idealists in politics. All country was thinking that way.
Of course we can't deny that so many good things have been done for this three years, in economical development of the country, today we have professional army and police, social system is improved and many other things. Results to compare what we had three years ago and today are phenomenal. I even can say that there is no one in today's opposition who can deliver and work with the same affectivity.
But problem is that Saakashvili's government is deeply corrupted as much as previous Shevardnadze's government, there is no democracy in the country. Most important democratic institutes like press, courts, judges all controlled and roiled by government. Everyone can be destroyed, killed or pressurised just because your view is different from official one or because somebody from the government don't like you. No matter you are political person or just normal citizen. There many examples like that...
I think there isn't whole information about real situation in Georgia outside of country. We haven't real democracy. It is only declared, but there is permanent breaking of human rights, increasing unemployment and poverty. Meanwhile We dream to become civilized, European country.
Mamuka, Tbilisi, Georgia
I have came just now from manifest... our 150 000 people were there and they were as one. today was the start of changes, but can you imagine our president left us and he flew somewhere for having meet with other like him people and presidents. we were waiting there for long hours but he didn't answer us, and at last he said that he will not change anything and he wants to be in same always. now news about school, he is selling schools, children houses, churches, trees, rivers, and beaches, and if you want to rest under the tree, you must pay for r it...
today happened one thing, when our manifest started, on the sky was showed cross by itself. there was white cross with huge size and i didn't have mobile for taking photo, and I wished to have it. this cross was for many hours on the sky. and many people were crying for seeing it. maybe God really wanted to show us something. hope everything will end without war.
many leaders are together now and they wanted to take people from other cities but this bad man made many problems for them, he sent to special people for cutting wheels, for beating drivers, the trains were not working and people couldn't come from far, the cars were broken, and people were afraid don't be killed and many of them were beaten , but they came as one, and they came by feet,
Madonna" writing from Tbilisi via her friend John Hartill, London, England