Tension continues to rise in Thailand's capital, Bangkok, after the dispersal of red-shirted government supporters following deadly clashes with opposition demonstrators.

Riot police fired tear-gas at protesters trying to force their way into the office compound of the prime minister, Yingluck Shinawatra, and Bangkok's police headquarters on Sunday.

Reporters saw anti-government protesters trying to destroy concrete barriers outside Government House. Police fired tear gas and water cannons to push them back. Separately, police drove back another crowd of protesters at the Bangkok police headquarters.

About 150 nervous-looking government supporters remained at Rajamangala Stadium in northeastern Bangkok early on Sunday morning, waiting for transport, Al Jazeera Online's Robert Kennedy reported.

An estimated 50,000 Red Shirts had converged on the site the night before.

Government officials have confirmed that four people died and 58 others sustained injuries in Saturday's violence.

The government supporters had been ordered to leave the stadium by Red Shirt leader Thida Thavornseth, who said it remained too dangerous after a night of violence between the rival groups.

The stadium was littered with plastic bags, and water and beer bottles, amid the heavy stench of rotting garbage and urine.

"Our leaders told us to go home because they were too worried that people would be killed or injured," said 56-year-old Aree Sawangjai, who travelled from the neighbouring province of Samut Sakorn to support the government amid the protests.

Outside the stadium, students from Ramkhamhaeng University opposed to the Red Shirts and the government blocked off roads to the area.

Lorries carrying medical workers were parked nearby on alert.

Across the city, anti-government protesters stormed a police sports complex on Sunday morning, amid plumes of tear gas, as Yingluck was swept away to safety by security forces.

She was now in a secure location which will remain undisclosed, an aide told Reuters news agency.

Siege of ministries

Al Jazeera's Wayne Hay, reporting from Bangkok on Sunday, said the dispersal of the Red Shirts may embolden the yellow-shirted opposition protesters.

"The anti-government group plan to take over 10 government facilities, and say today is the day that the government will fall," he said.

The protesters have been occupying several government ministries for the past week.

On Sunday morning, they took control of broadcaster Thai PBS, according to reports.

At the Royal Thai Police headquarters, several thousand protesters were blowing whistles and screaming at riot police behind a razor-wire barricade, Al Jazeera Online's Kennedy said.

"About 20 police officers who cordoned off Rama 1 Road were challenged by some 100 angry demonstrators. 'Go away slaves. Go away,' they shouted. Officers retreated across the street, satisfying the crowd, though taunts and jeers continued," he said.

The demonstrators are seeking to topple Yingluck's government, which they believe serves the interests of her brother Thaksin Shinawatra, who was toppled as prime minister by a 2006 military coup after being accused of corruption and abuse of power.

Yingluck's administration had been attempting to push through an amnesty bill, which many here believe would facilitate Thaksin's return to power.