Thai Prime Minister Yingluck Shinawatra has refused to step down, rejecting opposition calls for a "people's council" to appoint a new premier. Police have fired rubber bullets at protesters outside government buildings.
Prime Minister Yingluck Shinawatra rejected demands issued by anti-government protest leaders in a televised address on Monday, describing them as "unconstitutional."
"Anything I can do to make people happy, I am willing to do ... but, as prime minister, what I can do must conform with the constitution," Yingluck said in her first comments since peaceful protests turned violent over the weekend.
Yingluck said police would not use force against demonstrators, saying she would "open every door," to find a peaceful solution to the political unrest.
Within hours, however, Thailand's national security chief said rubber bullets were being used on protesters who had broken through concrete barriers set up around Government House, Yingluck's office in central Bangkok.
"We are alternating between the use of water cannons, tear gas and rubber bullets. Rubber bullets are being used in one area only and that is the bridge near Government House," Paradorn Pattanathabutr told the news agency Reuters.
Clashes were also reported around the Cabinet headquarters and the Metropolitan Police Bureau in western Bangkok, while dozens of schools and universities also remained closed because of security concerns.
Protest leaders set ultimatum
Yingluck's comments came a day after protest leader Suthep Thaugsuban told the prime minister that her resignation or new elections would not be enough to satisfy protesters. He called for an unelected "people's council" to pick a new leader.
"I told Yingluck that this will be our only meeting and we will not meet again until the people win," Suthep said. The protest leader set a Tuesday deadline for the premier, whom he accuses of being a puppet for her brother, former Prime Minister Thaksin Shinawatra, to resign. He also renewed his call for civil servants to strike.
"Stop working for the Thaksin regime and come out and protest," he said.
Protests had largely remained peaceful until the weekend, when at least three people were killed and 103 injured in clashes.
On Sunday, riot police used tear gas and water cannon to repel protesters seeking to take control of government buildings including an office used by the Cabinet's administration. Some 30,000 protesters were reported to be present, with some throwing rocks and petrol bombs at officers.
The crisis began on November 1, with Yingluck's ruling coalition trying to push through a bill in parliament that would have resulted in amnesty for her brother, as well as others convicted in politically related cases during 2004 and 2013. The bill was rejected by the country's Senate.
Thaksin Shinawatra - who was premier from 2001 until being ousted in a 2006 coup - has been living abroad since 2008. He faces a two-year jail sentence for abuse of power if he returns to Thailand.
Last week, the prime minister survived a no-confidence vote lodged by Thailand's opposition comparatively comfortably.
ccp/pfd (AFP, Reuters, AP, dpa)