Protestors gather in Urumqi in China's western Xinjiang region on Sunday. The government blamed exiled Uighurs, Muslims from western China, for stoking the unrest, while exile groups blamed police for using violence first. (Associated Press)

Tensions between ethnic Muslims and China's Han majority in the far western Xinjiang region erupted in riots that killed 140 people and injured 828, an official said Monday, marking the deadliest unrest to hit the volatile area in decades.

A peaceful protest Sunday of about 1,000 to 3,000 people in the regional capital, Urumqi, apparently spun out of control, as rioters went on a rampage and clashed with police.

The official Xinhua News Agency reported hundreds of people were arrested.

There was little immediate explanation for how so many people died.

A video grab from Xinjiang TV shows a crying woman carrying her baby near where riots occurred in Urumqi on Sunday. (Xinjiang TV/Reuteres)

The government blamed exiled Uighurs, Muslims from western China, for stoking the unrest. Exile groups said the violence started only after police began using force to crack down on a peaceful protest.

The demonstrators who gathered Sunday had been demanding justice for two Uighurs killed last month during a fight with their Han Chinese co-workers at a factory in southern China.

Accounts differed over what happened next in Urumqi, but the violence seemed to have started when a crowd of protesters refused to disperse.

Rioters overturned barricades, attacking vehicles and houses, and clashed violently with police, according to media and witness accounts.

State television aired footage showing protesters attacking and kicking people on the ground. Other people, who appeared to be Han Chinese, sat dazed with blood pouring down their faces.

Mobile phone service provided by at least one company was cut Monday to stop people from organizing further action in Xinjiang.

Longstanding tensions

Tensions between Uighurs and Chinese are never far from the surface in Xinjiang, China's vast Central Asian buffer province.

Uighur separatists have waged a sporadic campaign for independence in recent decades, and the military, armed police and riot squads maintain a visible presence in the region.

After a few years of relative calm, separatist violence picked up last year with attacks against border police and bombings of government buildings.