Thai "red shirt" protesters ruled out negotiations with the government on Sunday and said they would not give up their fight for early elections after clashes with security forces the previous day killed 21 people.

Bangkok was quiet on Sunday, but with no resolution in sight and the prospect of more violence, analysts said the stock market, one of Asia's most buoyant this year, was likely to take a hit when trading resumed on Monday.

"The time for negotiation is up. We don't negotiate with murderers," Weng Tojirakarn, a red shirt leader, told Reuters: "We have to keep fighting," he said, adding the protesters were not planning any action in Bangkok on Sunday "out of respect for the dead".

The red shirts, mostly rural and working-class supporters of ex-premier Thaksin Shinawatra who was ousted in a coup in 2006, are demanding that Prime Minister Abhisit Vejjajiva dissolve parliament immediately and leave the country.

Saturday's fighting, the worst political violence in the country in 18 years and some of it in well-known Bangkok tourist areas, ended after security forces pulled back late in the night.

The red shirts, still numbering in the thousands, have occupied two main areas of the capital, a city of 15 million. They made no attempt to come out of their bases on Sunday and troops did not make any move toward them.