Thousands of protesters have paralysed Lebanon with a general strike that led to street clashes in which three people were killed.
More than 100 people were injured as protesters fought with government supporters in the capital, Beirut, and other parts of the country.
The demonstrators blocked roads with burning tyres. Flights were cancelled and businesses closed.
The Hezbollah-led opposition called the strike and is urging fresh elections.
The protesters see the government as being too close to the West, and accuse it of bankrupting Lebanon.
In a televised speech, Prime Minister Fouad Siniora said he would stand firm against "intimidation" and "strife".
"Today's general strike turned into actions and harassment that overstepped all limits and rekindled memories of times of strife, war and hegemony," he said.
An opposition protester manning one of the burning barricades on Beirut's airport road told the BBC that "only America and Britain" want Mr Siniora to stay in office.
"We may be causing some pollution, but it's better to put up with that for a few days than to put up with the pollution of this government," he said.
There was little sign of a concerted move by the security forces to clear the barricades as the government had said they would, leading to allegations that the army and police were collaborating with the opposition, reports the BBC's Jim Muir in Beirut.
Many people joined the strike in the mainly Shia south and east of the country. In the north, among the Christians and Muslims, there are both supporters and opponents of the government, so tension has been particularly high, our correspondent says.
Opposition leaders have vowed no let-up in their campaign. Mr Siniora remains holed up in Government House, which has been besieged by Hezbollah supporters since 1 December.
Christian leader Samir Geagea told al-Jazeera television: "What is happening is the furthest thing from democratic means. This is direct terrorism to paralyse the country."
Balance of power
Hezbollah, which is backed by Syria and Iran, has been campaigning since the beginning of December to replace the Western-backed cabinet with a government in which it would have a veto.
The economy and trade minister, Sami Haddad, told the BBC the government had accepted the principle of a national unity cabinet - but he said it would not be dictated to by the opposition.
Mr Siniora still enjoys strong support from his loose alliance of Sunni Muslims, Christians and Druze, and is backed by powerful outside players, including the US, France and Saudi Arabia.
The BBC's Jim Muir says the struggle on the ground may be over barricades and roads, but it is also over the balance of power in the region.
The US failure in Iraq has apparently emboldened Syria and its strategic allies Iran to seek to redress the balance throughout the region, including in Lebanon.
Our correspondent says Hezbollah seems determined to translate its perceived success against Israel in last summer's war into a new status in the Lebanese power system, diluting or bringing down a government which it sees as being too close to the West.
Hezbollah supporters accuse the government of colluding with the Israeli onslaught in the hope that it would break the back of the Hezbollah forces, which the government wanted to disarm, but was powerless to do so, our correspondent says.