Thailand's authorities have put Bangkok and about a third of the country under curfew after street protest leaders surrendered.
At least 27 buildings were set ablaze after the red-shirt leaders' surrender and pockets of resistance remained despite pleas from leaders to go home.
Some 40 people have died since troops ringed the protesters last week, with at least six more deaths on Wednesday.
Fires were reported at the stock exchange, banks and a shopping mall.
AT THE SCENE
Continue reading the main story Alastair Leithead
Alastair Leithead BBC News, Bangkok
The main area at the heart of the commercial district is completely deserted. This morning there were women dancing and people on stage giving speeches.
All those hundreds of people who were in this main part of the protest site have gone.
People have set fire to buildings. There's a lot of smoke over the city, burning piles of debris.
Someone just told us there were very emotional scenes when the leaders came and said, "it's all over", and told people to go home.
But some hardline red-shirt protesters were holed up in an over-head railway station and they were clashing with the military.
About 900 soldiers and police were due to escort firefighters into the city centre to tackle the huge blaze engulfing Central World, one of South-East Asia's biggest shopping centres, a military source told AFP news agency.
Appearing on TV, Prime Minister Abhisit Vejjajiva said he was "confident and determined to end the problems and return the country to peace and order once again".