Chinese police shot and killed 14 people during a riot near the old Silk Road city of Kashgar in which two policemen were also killed, the local government said on Monday, the latest unrest in a region that has a substantial Muslim population.
China has previously called some of the violence in the far western region of Xinjiang the work of Islamist militants plotting holy war.
Describing the incident which happened late on Sunday, Hua Chunying, a spokeswoman for the Ministry of Foreign Affairs, stopped short of directly blaming Islamist militants but said a "violent terror gang" attacked police with explosives.
"It once again showed the true face of violent terror. It should be condemned by all people who love peace and stability," she told a daily news briefing. "This conspiracy does not enjoy popular support and is doomed to failure."
The regional government said police were attacked by a mob throwing explosive devices and wielding knives when they went to arrest "criminal suspects" in a village near Kashgar.
"Police responded decisively," the government said in a brief statement, adding that two people had been detained and that an investigation had been launched.
The official Xinhua news agency said in an English-language report that "terrorists" were responsible. It did not elaborate.
A police officer reached by Reuters in the county where the incident occurred, called Shufu county in Chinese, said it was "not convenient" to provide any additional information.
In a similar outburst of violence, at least nine civilians and two policemen were killed when a group of people armed with axes and knives attacked a police station also near Kashgar last month, state media has said.
Rights groups and exiles say police often use often heavy-handed tactics against the Muslim Uighur community, which calls Xinjiang home. Violence has broken out previously when groups of Uighurs protest at police stations, they say.
China has stepped up security in Xinjiang after a vehicle ploughed into tourists on the edge of Beijing's Tiananmen Square in October, killing the three people in the car and two bystanders.
China said the attack was carried out by Islamist militants, and has reacted angrily to suggestions that it was because of frustration and anger over government repression of Muslims in Xinjiang.
Many of Xinjiang's Turkic-speaking, Muslim people chafe at restrictions on their culture, language and religion, although the government insists it grants them broad freedoms.
Xinjiang has been the scene of numerous incidents of unrest in recent years, which the government often blames on the separatist East Turkestan Islamic Movement, even though many experts and rights groups cast doubt on its existence as a cohesive group.
Many rights groups say China has long overplayed the threat posed to justify its tough controls in energy-rich Xinjiang, which lies strategically on the borders of Central Asia, India and Pakistan.