Security forces fired shots in the air and used water cannons and tear gas to disperse about 2,000 angry Muslim youths rioting in Thailand's troubled south Monday, leaving at least six people dead and 12 injured, an official said.

A protest to demand the release of six detained security guards turned violent earlier Monday, with demonstrators hurling rocks at a police station in southern Narathiwat province's (search) Takbai district and overturning a military truck.

The rioters then tried to storm the building and a nearby district office during the six-hour melee. Police and soldiers responded by firing water cannons and tear gas, while shooting in the air to scatter the rioters.

"There are 12 injured and six dead," said Sirichai Pattananutaporn, Narathiwat's public health officer. He was unable to give more details about the deaths but said autopsy results would be available Tuesday. The casualties include one injured policeman.

One protester had been grazed by a bullet, said an emergency room official at Sungai Kolok hospital who asked not to be identified.

Local television footage showed soldiers dragging, kicking and hitting some of the protesters with their rifle butts. Near-constant gunfire can be heard in the background.

It also showed close-up footage of the body of a man who appeared to be dead, slumped over a cement planter with a large open wound on his head.

Meanwhile, the regional army commander, Lt. Gen. Pisarn Wattanawongkhiri, declared a curfew in the three southern provinces of Yala, Pattani (search) and Narathiwat from 10 p.m. (1500 GMT) to 6 a.m. (2300 GMT), until further notice.

Authorities earlier stepped up security in the area, deploying more than 1,000 police officers and soldiers.

The incident prompted Prime Minister Thaksin Shinawatra (search) to make an emergency trip to the area.

Thaksin said he wanted to visit the scene of the riot to "give the authorities moral support."

"I want to tell the Thai Muslims ... that I know about everything that goes on in the south, and I will absolutely not allow the authorities to harass the public," Thaksin told reporters. "But when the authorities set up laws, they have to be respected."

Southern Muslims have long complained about poverty and discrimination, especially in education and employment.

Yala, Pattani and Narathiwat — the only Muslim-dominated areas in predominantly Buddhist Thailand — have seen a wave of violence this year, with more than 360 people killed since January.

Authorities have blamed the bombings and drive-by shootings on a renewed separatist insurgency, which had died down after a government amnesty in the 1980s.