A plane bound for China's restive northwestern Xinjiang region was forced to land Thursday after a passenger claimed there was a bomb aboard, the official Xinhua news agency reported, citing officials.

Police detained the woman passenger after she threatened to detonate a bomb during the China United Airlines flight from Beijing to Xinjiang's capital Urumqi, Xinhua reported.

It did not say whether any explosives had been discovered on the plane, which made an emergency landing at Gansu's Jiayuguan Airport on Thursday evening.

"A woman threatened the plane staff, saying 'many people will die, there is TNT on the plane'," Xinhua quoted the Jiayuguan head of public security Chang Shaoyuan as saying.

Such incidents are rare in China, although in August 2009, a flight to Urumqi was forced to return to Afghanistan following a bomb threat, Xinhua reported earlier.

No one at the Beijing offices of China United Airlines -- which was founded by the Chinese army but is now a commercial operation -- could immediately be reached for comment.

Xinjiang -- a resource-rich and strategically vital region that borders eight countries -- is home to roughly nine million Turkic-speaking Uighurs who have long bridled under what many see as government oppression.

An influx of ethnic Han Chinese has fuelled anger, with some Uighurs complaining that Han get better jobs and pay and saying traditional Uighur culture is being deliberately diluted.

Two years ago, bloody ethnic riots in Urumqi killed 197 people and injured around 1,700.

Earlier this year the region's most senior official vowed to crack down on violence after a wave of unrest that killed at least 21 people, including eight suspects allegedly involved in the attacks.

An elite police counter-terror squad, the Snow Leopard Commando unit, was sent to the area in August and Zhang Chunxian, Communist Party chief for Xinjiang, vowed a "strike-hard policy in the crackdown against terrorists".

Beijing has blamed much of Xinjiang's unrest on the "three forces" of extremism, separatism and terrorism and said Pakistan-trained Muslim separatists were behind the latest attacks.

But some experts doubt that terror cells operate in Xinjiang, where Uighurs are Sunni and practice a moderate form of Islam.

They say the government has produced little evidence of an organised terrorist threat in the region, and argue its sporadic bouts of unrest stem more from long-standing local resentment.