Anti-government protestors set fire to at least 35 buildings in Bangkok in a rampage that followed a government crackdown against them that left up to 16 dead and 88 wounded, officials said on Thursday.

Demonstrators ran amok in central Bangkok on Wednesday after Thai troops stormed their protest site, prompting the demonstration’s top leadership to surrender.

By Thursday, calm returned to the capital after the worst violence Bangkok had seen in almost two decades, but authorities extended a nighttime curfew until Sunday morning to better guarantee security.

“We understand their frustration, but the violence that took place last night went beyond frustration,” government spokesman Panitan Wattanyakorn said of the protestors’ rampage. “It was organized crime, organized terrorism. We are working very hard now to contain these acts of terrorism.” Mr. Panitan said seven people died on Wednesday in the government crackdown on the protest site at Ratchaprasong, the central, upscale shopping and hotel district that the demonstrators had occupied since April 3, but acknowledged the government was investigating reports that nine bodies were found on Thursday at a temple there.

On Wednesday, thousands of protestors fled to the Buddhist temple to avoid government troops.

“They were shooting at us in the temple,” said Manat Kaetphet, 44, from Amnat Charoen province. “I saw six people get shot.” The government has offered free bus rides to take the protestors home. Many of them are from Thailand’s northern and north—eastern provinces.

Wednesday’s rioting began when protestors became incensed by the government’s crackdown and their leadership’s capitulation after failing to achieve their political goals despite clashes with authorities that had left an estimated 82 dead over the past two months of protests.

Their more militant elements went on a rampage in the city, attacking mostly outlets of business groups closely linked to the Thai establishment.

At least 35 buildings were set on fire on Wednesday night, the local government said.

Central World Department Store and a Big—C shopping outlet at Ratchaprasong were gutted after firefighters were prevented from reaching the burning buildings by protestors, a Bangkok government official said.

Both outlets belong to the Central Department Group, deemed a supporter of the “ammat,” or Thailand’s bureaucratic elite, vilified by the demonstration’s leaders, who painted their movement as a “class war” and “people’s revolution.” Protestors also set fire to 10 branches of the Bangkok Bank, another business group deemed close to the Thai establishment. The United Front for Democracy Against Dictatorship (UDD), as the protestors are officially called, started demonstrating in Bangkok on March 12 in a bid to force Prime Minister Abhisit Vejjajiva to dissolve parliament and hold new elections.

The protests started peacefully but turned nasty after the UDD raided Parliament on April 7, prompting the government to declare emergency law in the capital.

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