Thai troops fired rubber bullets and tear gas at thousands of demonstrators, who fought back with guns, grenades and petrol bombs in riots that killed 12 people, Bangkok's worst political violence in 18 years.
At least 521 people, including 64 soldiers and police, were were wounded in the fighting near the Phan Fah bridge and Rajdumnoen Road in Bangkok's old quarter, a protest base near government buildings and the regional UN headquarters.
Twelve people died, including three soldiers, an emergency medical centre said.
Among those killed was Reuters TV camerman Hiro Muramoto, a 43-year-old Japanese national who had worked for Thomson Reuters in Tokyo for more than 15 years and had arrived in Bangkok on Thursday to cover the protests.
Hundreds of "red shirt" protesters also forced their way into government offices in two northern cities, raising the risk of a larger uprising against Prime Minister Abhisit Vejjajiva and his 16-month-old, military-backed government.
Tension and uncertainty gripped the city of 15 million overnight, with protesters still on the streets and no sign of the government meeting demands for Abhisit to leave the country and an immediate dissolution of parliament. In a televised statement, Abhisit expressed regret to the families of the victims and said the army was only allowed to use live bullets "firing into the air and in self-defence".Bangkok
