Following daylong clashes between his supporters and police on Sunday, Suthep Thaugsuban, the leader of Thailand’s anti-government protests, said that he met Prime Minister Yingluck Shinawatra but defiantly told her he would accept nothing less than her resignation and a new government of an appointed council.

In a defiant tone that drew cheers from his supporters, Suthep Thaugsuban said the meeting with was held under the auspices of the military, which says it is neutral in the conflict.

Police in Thailand had fought off mobs of rock-throwing protesters armed with petrol bombs who tried to battle their way into the government’s heavily fortified headquarters on Sunday, as gunshots rang out in Bangkok and the Prime Minister fled a police complex during the sharpest escalation yet of the country’s latest crisis.

The protests, aimed at toppling Yingluck Shinawatra’s administration, have renewed fears of prolonged instability in one of Southeast Asia’s biggest economies. Sunday marked the first time police have used force since demonstrations began in earnest a week ago a risky strategy that many fear could trigger more bloodshed.

At least four people have been killed and 103 injured in skirmishes so far, according to police and the state’s emergency medical services. The deaths occurred at a Bangkok stadium where shooting was heard on Sunday for the second day and the body of one protester shot in the chest lay face-up on the ground.

The unrest forced several of the capital’s biggest and glitziest shopping malls to close in the heart of the city and snarled traffic. Mobs also besieged several television stations, demanding they broadcast the protesters’ views.

With skirmishes around Ms. Yingluck’s office at Government House continuing as darkness fell, the government advised residents to stay indoors overnight for their safety.

Ms. Yingluck spent the morning in meetings at a police complex but evacuated to an undisclosed locationafter more than a hundred protesters attempted to break into the compound, according to her secretary.

Several demonstrators, however, were unaware Ms. Yingluck was inside. Those who made it a few steps into the vast complex stayed only a few minutes and her secretary said they did not get anywhere near the heavily protected building where Ms. Yingluck was located.

“We want Yingluck to get out of power! She must go!” said Sothorn Kerdkaew, an agriculture student standing outside the police complex.

Political instability has plagued Thailand since the military ousted Yingluck’s brother, Thaksin Shinawatra, in a 2006 coup. The latest unrest began last month after a bid by Ms. Yingluck’s ruling Pheu Thai party to push an amnesty law through Parliament that would have allowed the return of her self-exiled brother Thaksin, who was overthrown after being accused of corruption and abuse of power. Mr. Thaksin lives in Dubai to avoid a two-year jail term for a corruption conviction he says was politically motivated. The Bill failed to pass the Upper House of Parliament.

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