BANGKOK (REUTERS) - Thai anti-government protesters vowed to demonstrate again on Monday and forge ahead with a "people's coup" campaign to topple Prime Minister Yingluck Shinawatra, a day after battling riot police outside her fortified office compound.

Protest leader Suthep Thaungsuban, 64, set a Tuesday deadline for Ms Yingluck, 46, to step aside and repeated his call for civil servants to go on strike on Monday. "Stop working for the Thaksin regime and come out and protest," he said.

Several major universities announced closures on Monday, citing the safety of students. The government has urged people in Bangkok, a metropolis of 10 million, to stay indoors from 10 pm to 5 am.

The protesters had set Sunday as "Victory Day" to oust the government but failed to achieve their goal of seizing the prime minister's office at Government House or occupying state buildings, despite intense clashes with riot police.

Police mostly held their lines, firing repeated rounds of tear gas and using water cannons against 30,000 protesters, many of whom hurled rocks and petrol bombs. Ms Yingluck was forced to flee a police compound to an undisclosed location.

It is the latest dramatic turn in a conflict pitting Bangkok's urban middle class and royalist elite against the mostly poor, rural supporters of Ms Yingluck and her brother Thaksin Shinawatra, a populist former prime minister ousted in a 2006 military coup.

Mr Suthep said he met with Ms Yingluck on Sunday but insisted there were no negotiations to end the worst political crisis since bloody political unrest in 2010.

"I told Yingluck that if police put down their weapons, we will welcome them as they are also Thai," he told supporters late on Sunday. "I told Yingluck that this will be our only meeting and we will not meet again until the people win."

The meeting, he said, was arranged by the military, a powerful institution that has publicly taken sides against Thaksin-allied governments in previous political crises but which has expressed neutrality in the current conflict.

A focal point in the protests is likely to remain Chaimaruchet Bridge, scene of intense skirmishes near Government House. By late Sunday, protesters had removed cement barriers, leaving just one razor wire-topped barricade between protesters and riot police.

Capping a week-long bid to topple Ms Yingluck and end her family's more than decade-long influence over Thai politics, Mr Suthep had urged supporters to seize government offices, television stations, police headquarters and the prime minister's offices in a "people's coup".

Protesters led by Mr Suthep, a deputy prime minister in the previous Democrat-led government that Ms Yingluck's party routed in a 2011 election, occupied a government complex on Thursday and the Finance Ministry on Monday. But they have struggled to seize more government buildings.

"They haven't seized a single place," National Security Council Chief Paradorn Pattanathabutr said of the protesters on Sunday. "They go to different places and they go back out."

Through Sunday, the detonation of stun grenades, followed by the jeers of protesters, echoed across the historic government quarter, not far from the Khao San Road tourist area, after a chaotic night of gun and knife battles in east Bangkok in which three people were killed and at least 58 wounded. Hospitals reported 46 people injured on Sunday.

Reuters journalists waiting to interview Ms Yingluck in the police Narcotics Suppression Bureau were told by an aide she had left after protesters made it inside the outer compound of the Police Sports Club, where the bureau is located.

The area around Government House was a scene of nearly non-stop skirmishes, as police fired teargas into a stone-throwing crowd chanting "Slaves! Slaves!" A Reuters photographer saw protesters hurl at least a dozen petrol bombs into police positions from Rajamangala University of Technology Phra Nakhorn across a canal from Government House.

Ms Yingluck, Thailand's first female prime minister, has called for talks with the protesters to end the protests, which have been joined by the opposition Democrats, Thailand's oldest political party. The Democrats have not won an election in more than two decades and have lost every national vote for the past 13 years to Mr Thaksin or his allies.

Mr Thaksin, who won over poor rural and urban voters with populist policies, was convicted in absentia of graft in 2008.

He dismisses the charges as politically motivated and remains in close touch with the government from his self-imposed exile, sometimes holding meetings with Ms Yingluck's cabinet by webcam.