"We are not allowing students to come and go because the situation is chaotic at the moment," Wang said. "All the students are at school, and we are taking care of them. But we are not clear about what's been going on outside."

China labels some Uighur separatist groups as terrorists.

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. The men were captured in Afghanistan and Pakistan in 2001, but the U.S. later determined they were not "enemy combatants."

Previous mass protests in Xinjiang that were quelled by armed forces became signal events for the separatist movement. In 1990, about 200 Uighurs shouting for holy war protested through Baren, a town near the Afghan border, resulting in violence that left at least two dozen people dead.

In 1997, amid a wave of bombings and assassinations, a protest by several hundred Uighurs in the city of Yining against religious restrictions turned into an anti-Chinese uprising that left at least 10 dead.

In both cases pro-independence groups said the death tolls were several times higher, and the government never conducted a public investigation into the events.