The demonstrators, who accuse Mrs. Shinawatra of being her brother’s puppet, are a minority who mainly support the opposition Democrat Party. They want to replace Mrs. Shinawatra’s popularly elected government with an unelected “people’s council,” but they have been vague about what that means.
Some of Sunday’s most dramatic scenes played out in front of Government House, where more than 1,000 protesters wearing bandanas and plastic bags over their heads hurled stones, bottles and sticks at police, who fought back with rubber bullets, water cannons and tear gas over barricades that separated them. Protesters clipped away at coils of barbed wire that surrounded the compound, pushed over barriers and at one point tried to drag one way with a green rope tied to a truck.
One Associated Press cameraman filming the mayhem was hit in the hand by a rock and the leg by a rubber bullet.
A few miles away, police drove back another crowd of protesters at the city’s police headquarters.
“We’re all brothers and sisters,” police shouted through a loudspeaker before firing tear gas. “Please don’t try to come in!”
Until this weekend, the demonstrations were largely peaceful. But tensions rose Saturday night after rival groups clashed in a northeastern Bangkok neighborhood where a large pro-government rally was being held in a stadium. Dozens were wounded, and unidentified gunmen were also responsible for the three shooting deaths.
Pro-government supporters left the stadium Sunday, but gunshots were fired again. It was not clear who was responsible or targeted, said police Col. Narongrit Promsawat.
Mrs. Shinawatra’s government, weary of past bloodshed, has gone to painstaking lengths to avoid using force. But it appeared to have drawn a red line at Government House and on Sunday fought back for the first time, both there and at the headquarters of Bangkok city police.
Gen. Prayuth Chan-ocha, the army commander, who said last week the army would not take sides — urged the police not to use force and also called on protesters to avert violence, according to Lt. Col. Winthai Suvaree, an army spokesman.
Most of the protesters are middle-class Bangkok residents who have been part of the anti-Thaksin movement for several years and people brought in from the Democrat Party strongholds in the southern provinces.
Because Mrs. Shinawatra’s party has overwhelming electoral support from the country’s rural majority, which benefited from her brother’s populist programs, the protesters want to change the country’s political system to a less democratic one in which the educated and well-connected would have a greater say than directly elected lawmakers.
• Associated Press writers Todd Pitman, Grant Peck, Jocelyn Gecker, Papitchaya Boonngok, Yves Dam Van and Raul Gallego Abellan contributed to this report.