URUMQI, China — Violence in the capital of China's volatile Xinjiang region killed 140 people and injured 828, an official said Monday, following rioting by members of a Muslim ethnic group and a police crackdown on their demonstrations.

The official toll makes the unrest the deadliest single incident of unrest in Xinjiang in recent decades.

The violence in Urumqi apparently happened after a peaceful protest Sunday of about 1,000 to 3,000 people spun out of control, with rioters overturning barricades, attacking vehicles and houses, and clashing with police.

Uigher exile groups said the violence started only after police began violently cracking down on the peaceful protest.

Wu Nong, director of the news office of the Xinjiang provincial government, said more than 260 vehicles were attacked or set on fire and 203 houses were damaged. He said 140 people were killed and 828 injured in the violence.

The official Xinhua News Agency also said 140 people died and that the death toll "was still climbing."

Tensions between Uighurs and the majority Han Chinese are never far from the surface in Xinjiang, China's vast Central Asian buffer province, where militant Uighurs have waged sporadic, violent separatist campaign. The overwhelming majority of Urumqi's 2.3 million people are Han Chinese.

State television aired footage that showed protesters attacking and kicking people on the ground. Other people 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.

The protest started Sunday with demonstrators demanding a probe into a fight between Uighurs and Han Chinese workers at a southern China factory last month. Accounts differed over what happened next in Urumqi, but the violence seemed to have started when a crowd of protesters — who started out peaceful — refused to disperse.

Uigher exile groups said the violence started when Chinese security forces cracked down on the peaceful protest.

"We are extremely saddened by the heavy-handed use of force by the Chinese security forces against the peaceful demonstrators," said Alim Seytoff, vice president of the Washington-based Uyghur American Association.

"We ask the international community to condemn China's killing of innocent Uihgurs. This is a very dark day in the history of the Uighur people," he said.

The association, led by a former businesswoman now living in America, Rebiya Kadeer, estimated that 1,000 to 3,000 people took part in the protest.