The violence began close to midnight Saturday when, according to the reports in state media and on a local government website, two members of the indigenous Uighur ethnic minority hijacked a truck, stabbed the driver to death and plowed it into a crowd at a night market.

The state-run Xinhua news agency said the two men then jumped out of the truck and stabbed six people to death and injured 28 others with knives before the crowd turned on the attackers, one of whom was killed and the other one captured alive by police.

Shortly before the attack, two blasts were heard in the city, Xinhua said, without giving further details.

On Sunday, three more people, including a police officer, were killed in further violence in Kashgar, according to Xinhua. It initially reported that the victims were killed in a bomb blast, but later quoted witnesses saying they had been "hacked to death by the rioters."

Xinhua said that police had shot dead what it said were four suspects, detained four others, and were still hunting for four more on Sunday.

Neither Xinhua nor the local government website said whether the attackers' victims were also Uighurs, or members of China's dominant Han ethnic group.

A local official who answered the telephone at Kashgar's police headquarters said she had no knowledge of the incident and then hung up. Other local officials didn't answer telephone calls.

Uighur groups have for decades waged a sporadic, sometimes violent, struggle for independence from Beijing, which they accuse of plundering the oil-rich region's resources, suppressing religious freedoms, and swamping it with ethnic Han Chinese migrants.

Beijing regards such groups as part of a terrorist organization with links to al Qaeda, and has courted international support for its campaign against them.

Elsewhere, ethnic Mongolians in Inner Mongolia, east of Xinjiang, staged rare protests in May over the hit-and-run killing of a Mongolian herder by a Han Chinese truck driver, who was swiftly tried and sentenced to death.

In July, China's government also conducted a major security clampdown and propaganda drive in Tibet, south of Xinjiang, to ensure stability for official celebrations to mark the 60th anniversary of what Beijing refers to as the "peaceful liberation" of the region by Communist forces in 1951. China says Tibet has been part of its territory for centuries and regards the Dalai Lama, who fled into exile in India in 1959, as a separatist, although he says he is campaigning peacefully for greater autonomy and cultural and religious freedoms, rather than independence.

The violence in Kashgar comes just under two weeks after police shot dead 14 Uighur rioters in the city of Hotan, also in Xinjiang, after they attacked a police station, setting fire to it and killing two police officers and two civilians, according to state media.

Local officials have blamed that attack on Uighur separatists, but the Germany-based World Uyghur Congress has denied the government's account and accused police in Hotan of killing 20 civilians protesting over a spate of recent arrests of young local men.

That incident was the bloodiest in Xinjiang since rioting between Uighurs and ethnic Han Chinese settlers left nearly 200 dead in the regional capital, Urumqi, in 2009, in one of the worst known cases of interethnic violence in modern China's history.

The World Uyghur Congress said Sunday it was still trying to contact local people in Kashgar to confirm details of the weekend's unrest, but initial reports suggest that Uighurs had attacked government personnel and some ethnic Han Chinese.

"At the moment it's too early to say, but something has happened and some people were killed," said Dolkun Isa, the general secretary of the World Uyghur Congress.

"What is true is that because of persecution and illegal detentions, of course people are angry with that and some people want justice. If they can't find a legal way, maybe they try this kind of violence. It is wrong Chinese policy towards Uighurs this is the main reason."