China's far western region of Xinjiang was investigating an explosion which killed or injured around 100 people, and police said on Saturday it was too early to determine the cause.

A truck carrying explosives blew up in the western suburbs of Urumqi, the region's capital, on Friday night, state media and police said.

The Xinhua said the explosives had been intended for disposal, suggesting an accident.

Xinjiang has been rocked by a series of bombings, riots and assassinations by the ethnic Uighur minority against the Chinese authorities since 1996.

A regional police official said it was too early to give an exact toll of the dead and injured, or determine the cause of the blast. The official Xinhua news agency said about 100 people were killed or injured.

``Initial analysis showed the truck was carrying explosives but the specific cause is not very clear,'' he said. ``Police have been busy for an entire night at the scene of the accident.''

The explosives detonated as the vehicle was on the city's Xishan Road at 7:30 p.m., damaging more than 20 other vehicles and nearby houses, Xinhua said.

China maintains a heavy military presence in the vast, sparsely inhabited border region and Xinjiang is also home to mining operations which could use explosives.

Local government officials and city police declined to comment on the case.

China has cracked down hard on the Uighur minority group and in July executed three men it said were separatists linked to a ''reactionary Muslim organization'' involved in making bombs.

A vehicle carrying explosives blew up and killed about 100 people on Friday in the suburbs of Urumqi, capital of west China's Xinjiang Uygur Autonomous Region, Xinhua news agency reported.

The agency, quoting sources at the Ministry of Public Security in the city, did not give the exact number of people killed. It said a number of people were injured.

The explosives being carried had been intended for disposal, the sources said. They detonated as the vehicle was on the Xishan Road in the western suburbs of Urumqi at 7:30 p.m., damaging more than 20 other vehicles and nearby houses.

Local police were clearing the site of the explosion and helping the injured, Xinhua said, adding that the cause of the explosion was under investigation.

The vast, sparsely inhabited Xinjiang region, largely desert, has many Chinese military and nuclear installations and civilian mining.

Muslim Uygurs who speak a Turkic language make up much of its population and the region has been rocked by riots, bombings and assassinations against the Chinese authorities and ethnic Chinese immigrants since 1996.

Uygur militants have been struggling for decades to establish an independent state they call East Turkestan in Xinjiang, which borders Afghanistan, Pakistan and three former Soviet Central Asian republics.

Chinese authorities said on Saturday they did not know what caused a major explosion which killed 60 people in the western region of Xinjiang, which has a history of separatist violence.

A truck carrying explosives blew up in the western suburbs of the region's capital Urumqi on Friday night, also injuring 309.

Local television showed ambulances and fire trucks lining the street as smoke rose in the distance. Soldiers in camouflage uniforms carrying stretchers and a group of nurses rushed toward the scene.

Xinhua said the explosives had been intended for disposal, suggesting an accident.

But analysts said the government would need to investigate if members of the ethnic Uighur minority agitating for a separate state might have played a role.

``I wouldn't be surprised if it was one of the fundamentalist groups,'' said Bruce Esposito, professor of East Asian history at the University of Hartford in the United States and a specialist on the region.

``They're attempting to be noisier, they are certainly attempting to be more prominent in Soviet Central Asia.''