BEIJING (AFP) - Chinese President Xi Jinping has called for stability in the ethnically-divided region of Xinjiang after clashes this week killed 21 people, state media reported on Friday.

Mr Xi's comments came after 15 police and social workers were killed in violence on Tuesday, as well as six members of the mostly Muslim Uighur minority suspected of "terrorist plotting", local officials said.

Mr Xi gave instructions on "how to handle the case, deal with the aftermath, and maintain stability in Xinjiang", the state-run Global Times said on its website, citing a local report, and without quoting Mr Xi's remarks directly.

The comments from China's top leader reflect high-level worries about long-standing unrest in the region which authorities often blame on "terrorism" - claims which rights groups say are used to repress minorities.

A specialised anti-terrorism unit of China's People's Liberation Army (PLA) carried out drills in the province this month, the PLA Daily reported.

The attack prompted a heated exchange between China and the United States after Washington said it was "deeply concerned" by accounts of discrimination against Uighurs and other Muslims in China.

China accused the US of a "double standard" for not condemning the attack despite being a victim of terror itself.

Riots between Uighurs and members of China's Han ethnic majority in Xinjiang's capital Urumqi in 2009 killed around 200 people, leading the ruling Communist Party to tighten surveillance and boost investment in the region.

Xinjiang, a region about twice the size of Turkey, is home to around nine million ethnic Uighurs, accounting for 46 per cent of the local population.

Another 39 per cent are members of China's Han majority.