Police in Kenya have fired bullets and tear gas in clashes with opposition party supporters who were defying a ban on protests over disputed elections.
Clashes broke out Nairobi, Mombasa and in western Kenya, where at least two people were killed.
Opposition leader Raila Odinga tried to reach a rally at Nairobi's Uhuru Park but was forced back by tear gas.
His Orange Democratic Movement (ODM) had called three days of protests over December elections it says were rigged.
President Mwai Kibaki was declared the winner but the results were rejected by the opposition and called into question by international observers.
More than 600 people have died in unrest since the polls. The violence has also driven about a quarter of a million from their homes and shaken relations between the country's dominant ethnic groups.
Mr Odinga was among a group of ODM leaders and activists who tried to make their way to the politically symbolic Uhuru (Freedom) Park.
The BBC's Caroline Karobia says police fired tear gas to stop their approach.
Mr Odinga was in a car, surrounded outside by several high-ranking ODM leaders and young supporters.
As the canisters landed, they all fled and were pursued by police down side streets, she says.
As the tension heightened at the entrance to Uhuru Park, anti-riot police, some riding on horses, charged at journalists and lobbed tear gas canisters to disperse them.
Many shopkeepers in the capital boarded up their properties to try to prevent looting, and business was at a standstill.
But correspondents say rain in Nairobi has stopped many people taking to the streets.
However, residents in the city's Kibera slum have told the BBC that three people were being treated for gunshot wounds.
Police denied firing at crowds in the area.
Mr Odinga said: "The massive deployment of security forces will not intimidate the people of Kenya from demanding their right, it is an indication that the government is terrified of its own people."
The BBC's Karen Allen in the western town of Kisumu, home to ODM presidential challenger Mr Odinga, says some 300 people were trying to march into the town centre when police opened fire.
Our correspondent says two bodies were carried away from the scene of the protest.
In the port city of Mombasa, there have also been running battles between protesters and police and several people have been injured.
Protesters carried a coffin to symbolise the "death of democracy"
A BBC correspondent there said opposition activists wearing white ribbons and carrying placards staged sit-ins at the main roads leading into the city.
In the western opposition stronghold of Eldoret, which witnessed the burning of a church in post-poll violence, protesters also erected roadblocks on the outskirts of town.
As the protests began, Mr Odinga said through "peaceful people power" and international mediation, his party would ensure that the political stalemate in the country was resolved.
Attempts at outside mediation between Mr Odinga and President Kibaki have failed with the latest, a bid by Kofi Annan, postponed when the former United Nations chief fell ill.
At Tuesday's inauguration of the new parliament, Kenya's two bitter rivals studiously ignored each other, correspondents say.
Parliament's new speaker, the ODM's Kenneth Marende, told the BBC that the ODM had the constitutional right to protest against Mr Kibaki's re-election.
He said the opposition's dominance of parliament would make it difficult for President Kibaki's PNU party to impose itself, and that it might be forced into forming a coalition.
Kenya's Foreign Minister Moses Wetangula told Reuters the ODM should keep its battle within parliament.
"We expect the strong opposition we have now in parliament to provide critical, effective oversight of the government, to audit government in every way," he said.