A clash between authorities and assailants has left 21 people dead in an act of terrorism, local government in China's restive Xinjiang region says, according to Belfast Telegraph.

The Xinjiang government propaganda office said that 15 officers and local government officials were among the dead after Tuesday April 23 afternoon's clash. It said six assailants were killed and another eight were captured.

The death toll was the highest in months in Xinjiang, which sees recurrent outbreaks of violence pitting members of the indigenous Turkic Muslim Uighur ethnic group against the authorities and majority ethnic Han Chinese migrants.

Rioting in July 2009 between Uighurs and Han killed nearly 200 people in Xinjiang's capital, Urumqi, and there have been sporadic attacks since, all of them quickly suppressed with overwhelming force by local paramilitary units.