At least 156 people were killed in in rioting by a Muslim ethnic group in China's far west, state media said Monday.
The brief report from Xinhua news agency gave no more details.
Protesters, mostly from the Uighur ethnic group, set dozens of cars on fire and attacked buses in several hours of violence in the Xinjiang province city of Urumqi on Sunday. The violence appeared to subside as the police and military presence intensified into the night, according to participants and witnesses.
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 appeared to show 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 an investigation into a fight between Uighurs and Han Chinese workers at a southern China factory last month. Accounts differed over what happened next in Xinjiang's capital of Urumqi, but the violence seemed to have started when a crowd of protesters — who started out peaceful — refused to disperse.
State media first reported at least 37 people — both Uighur and Han Chinese — were hospitalized with injuries. Now, reports indicate that 828 people have been injured.
Adam Grode, an American Fulbright scholar studying in Urumqi, said he heard explosions and also saw a few people being carried off on stretchers and a Han Chinese man with blood on his shirt entering a hospital.
He said he saw police pushing people back with tear gas, fire hoses and batons, and protesters knocking over police barriers and smashing bus windows.
"Every time the police showed some force, the people would jump the barriers and get back on the street. It was like a cat-and-mouse sort of game," said Grode, 26.
The government's Xinhua News Agency quoted unnamed officials saying that at least three ethnic Han Chinese were killed in the violence, in which the crowd attacked passers-by, torched vehicles and interrupted traffic on some roads. It later said an unknown number of people were killed, including the policeman.
"The violence is a pre-empted, organized violent crime. It is instigated and directed from abroad and carried out by outlaws in the country," said a government statement carried by Xinhua.
Kadeer's spokesman, Alim Seytoff, said by telephone from Washington, D.C., that the accusations were baseless.
"It's common practice for the Chinese government to accuse Ms. Kadeer for any unrest in East Turkestan and His Holiness the Dalai Lama for any unrest in Tibet," he said.
Uighur rights groups and militants demanding an independent Xinjiang often refer to the sprawling region of deserts and mountains, which borders eight Central Asian nations, as "East Turkestan."
The clashes Sunday in Urumqi echoed last year's unrest in Tibet, when a peaceful demonstration by monks in the capital of Lhasa erupted in riots that spread to surrounding areas, leaving at least 22 dead. The Chinese government accused the Dalai Lama of orchestrating the violence — a charge he denied.
Seytoff also read a brief statement from Kadeer: "The real cause of the problem lies with the Chinese government's policies toward the Uighurs. It's not alleged instigation by me or some outside forces."
The demonstration started peacefully with more than 300 people staging a silent sit-down protest in People's Square in Urumqi to demand an investigation into the June 25 brawl at a toy factory in southern China, said Gulinisa Maimaiti, a 32-year-old employee of a foreign company who took part in the protest.
Xinhua said two died in last month's factory melee in southern Guangdong province, others say the real figure was higher.
Gulinisa said in a phone interview that the crowd grew to 1,000 people, and when they refused to disperse, police pinned protesters to the ground before taking 40 protesters away.
Video shot from a building nearby and photos from mobile phones showed people running from police and a car on fire. In other shots, smoke rises in the distance and fire engines race to the protest.
The Urumqi police and city government would not comment about the incident.
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.
Four Uighur detainees at the U.S. prison at Guantanamo Bay in Cuba were recently released and relocated to Bermuda despite Beijing's objections because U.S. officials have said they fear the men would be executed if they returned to China. Officials have also been trying to transfer 13 others to the Pacific nation of Palau.