BEIJING (AP) - Chinese police killed 12 people during July 5 rioting in the western city of Urumqi, officials said - a rare acknowledgment by the government that security forces opened fire in the worst ethnic clashes to hit the region in decades.

The unrest began when a peaceful protest by Muslim ethnic minority Uighurs turned violent after it was stopped by police. The Uighurs went on a rampage in the capital of Xinjiang province, smashing windows, burning cars and beating Han Chinese, the nation's dominant ethnic group.

Two days after the first rioting, vigilante groups of ethnic Han took to the streets and attacked Uighurs.

Xinjiang Governor Nur Bekri said police shot the "mobsters" on July 5 after first firing warning shots, according to a report late Saturday by the official Xinhua News Agency. He apparently did not say which ethnic group the "mobsters" belonged to.

"The police showed as much restraint as possible during the unrest," Bekri was quoted as saying, adding that many police officers were injured and one was killed.

An official surnamed Wu from the Xinjiang regional government information office confirmed the report Sunday. Wu could not say if those killed by police were Uighurs or Han Chinese.

The governor said three of them died on the spot and nine died after treatment failed.