A tour bus has plunged into a Tibetan valley after hitting two vehicles, killing 44 people and injuring 11, China's official news agency Xinhua reported.

"The 55-seat bus carrying 50 people fell off a 10-metre-plus-high cliff after crashing into a sports utility vehicle and a pick-up truck," the report said, citing the regional government on Saturday.

Another five people were in the other vehicles in the accident which happened at around 4:25pm (08:25 GMT) in Nyemo County, west of the capital Lhasa, in the Tibet Autonomous Region which is governed by China.

The bus passengers were mainly tourists from eastern China. The injured were being treated at hospitals in Lhasa and did not have life-threatening injuries, Xinhua said.

Pictures on the news agency's website showed rescue workers at the bus which was lying with its wheels in the air.

Fatal road accidents are a serious problem in China, particularly involving the country's often over-crowded long-distance buses.

In August 2012, at least 36 people died when a double-decker sleeper bus slammed into the rear of a methanol tanker and burst into flames in northern China.