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

Xinjiang Governor Nur Bekri said in a televised address early Monday that Uighur exiles led by Kadeer of caused the violence, saying, "Rebiya had phone conversations with people in China on July 5 in order to incite, and Web sites such as Uighurbiz.cn and Diyarim.com were used to orchestrate the incitement and spread propaganda."

A government statement quoted by Xinhua said the violence was "a pre-empted, organized violent crime. It is instigated and directed from abroad and carried out by outlaws in the country."

Ilham Tohti, a Uighur economics professor at Central Nationalities University in Beijing and founder of Uighurbiz.cn — one of the implicated Web sites — said "the relevant authorities" were questioning him about his Web site.

His site has become a lively forum for many issues about Chinese rule in Xinjiang.

Xinjiang's top Communist Party official, Wang Lequan, called the incident "a profound lesson learned in blood" and said authorities "must take the most resolute and strongest measures to deal with the enemies' latest attempt at sabotage."

"We also must expose Rebiya and those like her ... we must tear away Rebiya's mask and let the world see her true nature."

Seytoff dimissed the accusations against Kadeer. "It's common practice for the Chinese government to accuse Ms. Kadeer for any unrest" in Xinjiang, he said.

The clashes Sunday in Urumqi echoed last year's unrest in Tibet, when a peaceful demonstration by monks in the capital of Lhasa erupted into riots that spread to surrounding areas, leaving at least 22 dead. The Chinese government accused Tibet's exiled spiritual leader, the Dalai Lama, of orchestrating the violence — a charge he denied.

Seytoff said he had heard from two sources that at least two dozen people had been killed by gunfire or crushed by armored police vehicles just outside Xinjiang University.

Mamet, a 36-year-old restaurant worker, said he saw People's Armed Police attack students outside Xinjiang University.

"First they fired tear gas at the students. Then they started beating them and shooting them with bullets. Big trucks arrived, and students were rounded up and arrested," Mamet said.

Wang Kui, an official with the Foreign Affairs Department at the university, said she aware of no such incident. She said no students from the university were among those killed or injured.