BANGKOK — Skirmishes between police and rock-throwing protesters killed at least four people and injured more than 100 Sunday, when mobs swarmed government offices, TV stations and police headquarters in an escalation of weeklong efforts to oust the prime minister.
Gunshots rang out at a Bangkok stadium, where the deaths occurred, and Prime Minister Yingluck Shinawatra was forced to flee a meeting with security officials at police headquarters when protesters attempted to storm the facility, apparently unaware that she was inside.
The increasingly violent protests have generated fears of instability in Thailand, one of the biggest economies in Southeast Asia and a key non-NATO ally of the U.S.
Sunday marked the first time police used force to quell protests since the demonstrations against the Yingluck administration began last week.
Short of establishing a curfew, Thai authorities advised Bangkok residents to stay indoors overnight Sunday to avoid injury.
"After 10 p.m. until 5 a.m., if it is not necessary, we ask people to not leave their homes, for their safety, so they will not become victims of provocateurs," Deputy Prime Minister Pracha Promnok said in a televised announcement.
Protesters have demanded that Ms. Yingluck, 46, resign her office, calling her a "puppet" of her billionaire brother — former Prime Minister Thaksin Shinawatra, who was deposed in a 2006 military coup. Ms. Yingluck had backed an amnesty bill that many said would have absolved her brother, who exiled himself to avoid a two-year prison sentence for a corruption conviction.
Protest leader Suthep Thaugsuban, 64, a former lawmaker for the opposition Democrat Party, met Sunday with Ms. Yingluck to demand her resignation and the dissolution of parliament to save the country from "bad politicians."
"He said the problem could be resolved only when she returned the power to the people to form the 'people's council' [that could] appoint a 'people's government' to rule the country," according to a report by the Thai Public Broadcasting Service.
Ms. Yingluck, who was elected in 2011 after weeks of protests that left scores dead, has refused demands to call an election. Before Sunday's skirmishes, she was hesitant to authorize the use of force by her country's U.S.-trained security units.
The Obama administration, which has said it is redirecting attention and resources to Asia, has been mostly quiet about the unrest in Thailand.
Hundreds of protesters hurled firecrackers and rocks Sunday at police, who responded with tear gas and water cannons to stop mobs from attacking the prime minister's empty Government House office, which is ringed with barbed wire and barricades.
Some protesters intimidated several TV stations into broadcasting anti-government propaganda Sunday night. Others failed in their plans to lay siege at police headquarters and the ministries of Foreign Affairs, Commerce, Interior, Labor and Education, as well as other official buildings.
The Finance Ministry and some other government offices, however, remained under the control of protesters throughout the weekend.
During the past week, Suthep supporters swarmed the Justice Ministry's Department of Special Investigation, Thailand's version of the FBI. Protesters chained its doors Saturday to prevent officials from working after the department recommended indictments against Mr. Suthep and former Prime Minister Abhisit Vejjajiva, who leads the Democrat Party, the nation's oldest political party.
Last month, the attorney general's office charged Mr. Suthep and Mr. Abhisit with premeditated and attempted murder in connection with the government's 2010 deadly crackdown on pro-democracy Red Shirt protesters. Mr. Suthep was deputy prime minister for security at the time, when the military unleashed its firepower on mostly civilian demonstrators.
Prosecutors said they would indict both men on Dec. 12. Mr. Suthep and Mr. Abhisit have denied any wrongdoing.
Mr. Abhisit, 49, lost the 2011 election to Ms. Yingluck, leader of the ruling For Thais party.
Mr. Suthep announced last week that he would stop the protests if he could disband parliament and become secretary-general of a right-wing "people's council" that would "pick a good man to be the prime minister, good men to be ministers."
He is backed by a right-wing militant Buddhist organization called the Dhamma Army, as well as students, workers and others mostly from Bangkok's middle class.
Opposing them are supporters of Ms. Yingluck and Thaksin, including the mostly lower-class Red Shirts, who helped Ms. Yingluck win in 2011.
The Reds expect Ms. Yingluck and her autocratic brother to continue rewarding them with populist policies, including cheap credit, health care and rice subsidies.
The protests highlight the rise of Thaksin and his family's "new money" backed by wealthy cronies and the grass-roots Reds. In some ways, they have challenged the establishment's royalist "old money."
But the opposing sides share similarities, making the clash partly a power grab by opportunistic rivals seeking to settle personal grudges and betrayals.
Thaksin was prime minister from 2001 to 2006, when he was toppled in a bloodless coup, and he is widely believed to influence his sister's administration from afar.
He wants to return to Thailand but is dodging a two-year prison term imposed by a post-coup court for a conflict of interest real estate deal involving his politically powerful former wife.
Thaksin also wants the return of $1.2 billion in cash and assets that a post-coup court seized because of his profits from a tax-free telecommunications deal.
Ms. Yingluck's government recently tried but failed to arrange an amnesty to erase several years of politically related criminal charges and convictions against Thaksin and others.
Her government also recently failed to amend the post-coup constitution, which demands that half the Senate be appointed in the bicameral parliament, limits the power of elected officials and grants vast powers to appointed judges.