A bruised Bangkok awoke Thursday to scenes of burned out and looted buildings in the wake of a deadly army assault on anti-government protests in the Thai capital.
 

Smoke billows from a commercial area of Bangkok where Red Shirt demonstrators had their camp. (AFP/Manan Vatsyayana)

Enraged protesters went on the rampage Wednesday, setting fire to major buildings including the stock exchange after the army moved in to break up a weeks-long rally by the "Red Shirt" demonstrators.

Plumes of black smoke billowed across the skyline in the aftermath of the military crackdown on the camp that left at least seven people dead, including an Italian journalist, and forced their leaders to surrender.

While most demonstrators dispersed, some militant protesters set fires at 27 locations in the capital in an upsurge of violence that prompted authorities to declare a night-time curfew across about a third of the country.

Prime Minister Abhisit Vejjajiva, who has been under enormous pressure to end the crippling standoff, said he intended to "get through" the crisis and return peace to the country.

"The end of the rally has dissatisfied some protesters, especially those who are armed," he said. "So they created trouble, particularly arson in some areas."

Major blazes swept through Central World, one of Southeast Asia's largest shopping centres, the Stock Exchange of Thailand, a downtown cinema, many banks and a television station where about 100 staff had to be rescued.

The bloody crackdown inflamed unrest outside the capital as supporters in northeast Thailand set fire to at least two provincial halls.

Violence also broke out in northern Chiang Mai where people tried to burn buildings and throw home-made bombs after the Bangkok protests ended, but by late evening the situation was under control, local officials said.

The government imposed an overnight curfew in Bangkok and almost a third of the country's 76 provinces, in a bid to quell the eruption of violence, admitting that parts of the capital were still outside their control.

"We are waiting until the people go back home, then we will deal with rogue protesters," Defence Minister General Prawit Wongsuwon told AFP.

The latest unrest began when armoured vehicles backed by armed troops firing live rounds smashed through towering barricades made of tyres and razor wire that the Red Shirts had erected around their sprawling base.

A tearful protest leader later announced on stage that the Reds would end their occupation of the upscale shopping and hotel district in the heart of the capital where they have been camped for six weeks.

"I know this is unacceptable to some of you... but we cannot stand this cruelty," said top Red Nattawut Saikuar. "We will exchange our freedom with your safety. We have tried our best."

At least four top Reds later went to the police headquarters nearby to give themselves up. The government said earlier some others had already fled.

An Italian freelance photographer, Fabio Polenghi, 45, was among those shot dead during the clashes at one end of the Reds' encampment, which had stretched for several kilometres (miles).

Several other journalists were wounded in the clashes, including Dutch television reporter Michel Maas who was shot in the shoulder.

Another journalist, a Canadian, and four soldiers were also badly injured by grenade attacks inside the camp.

An AFP photographer saw two protesters lying dead on the ground after being shot in the head when troops pushed into the encampment. At least 46 people have died since the army moved to lock down the area last Thursday.

Police said elite troops had orders to shoot on sight anyone looting, committing arson or inciting unrest, following several days of intense clashes in the capital.

"Tonight will be another night of suffering," government spokesman Panitan Wattanayagorn said in an address on national television.

The United States urged Thai protest leaders to rein in their supporters following the bloody army crackdown.

Washington was "deeply concerned that 'Red Shirt' supporters have engaged in arson, targeting electricity infrastructure and media outlets and have attacked individual journalists," said State Department spokesman Gordon Duguid.

The Reds have been campaigning for elections to replace Abhisit's administration, which they consider illegitimate because it came to power with the backing of the army in a 2008 parliamentary vote.

The crisis has left at least 75 people dead and about 1,700 wounded since mid-March, including 25 people who died in a failed army crackdown on April 10.

The Reds are mostly supporters of fugitive ex-premier Thaksin Shinawatra who was ousted in a 2006 coup.

Thaksin -- accused by the government of bankrolling the protests and inciting unrest -- denied Wednesday he had undermined peace talks, saying he was not the "mastermind of the terrorists".