A mob of anti-government protesters attacked at least two people they suspected of supporting the current Thai government and smashed the windows of a moving Bangkok bus Saturday in the first eruption of violence after a week of tense street protests.
The mob also smashed the windshield of a taxi carrying people wearing red shirts, a sign of government support.
The violence erupted when the crowd of more than 1,000 people led by university students who oppose the government tried to block people from entering a stadium where supporters of Prime Minister Yingluck Shinawatra were holding a rally.
The national police gave televised reaction immediately, highlighting the fears of wider violence breaking out in the bitterly divided country.
"The situation has almost returned to normal. About 100 police officers are taking care of the situation," police spokesman Maj. Gen. Piya Uthayo said.
The clashes came after a week of dramatic protests against Yingluck's government, which included seizing the Finance Ministry, turning off power at police headquarters and camping at a sprawling government office complex.
Protesters vowed to turn up the pressure Sunday by seizing more government ministries and key offices, including the Government House, which is the prime minister's office compound.
Saturday's violence was isolated to an area in northeastern Bangkok outside of Rajamangala Stadium, where "Red Shirt" supporters were gathering to show their support for Yingluck. But it was bound to increase tension and raise concerns of new political turmoil and instability in Thailand.
The crowd first attacked two men, one of whom was pulled off the back of a motorcycle and punched and kicked. Both men were seen being pulled away by security and treated for head injuries.
Later, the crowd surrounded a taxi believed to be carrying people wearing red shirts and shattered the windshield before the taxi was able to drive away.
Police then moved in and the students began to retreat to their nearby university but then spotted a bus carrying some passengers wearing red shirts and chased after it.
The students threw stones at the bus and then began hitting it on all sides with sticks, shattering or breaking the buses windows as terrified passengers inside dropped to the floor. It was not immediately clear if anyone on the bus was injured before it moved away.
Protest leaders backed by the opposition say they want to uproot the political machine of former Prime Minister Thaksin Shinawatra, Yingluck's brother, who was ousted by a military coup in 2006 for alleged corruption and abuse of power.
The protesters accuse Yingluck of being a puppet of her billionaire brother.
Thaksin, who lives in Dubai to avoid a two-year jail term for a corruption conviction he says was politically motivated, is a highly polarizing figure in Thailand. An ill-advised bid by Yingluck's ruling Pheu Thai party to push an amnesty law through Parliament that would have allowed his return sparked the latest wave of protests.
Associated Press writers Jocelyn Gecker and Raul Gallego Abellan contributed to this report.