A coal truck and a bus collided head-on Tuesday on a Chinese highway in northwest Xinjiang-Uyghur region, killing at least 21 people, sources told Xinhua.

The accident on National Highway 314 injured 12 others, three of them seriously, the report said.

It quoted one source from the region's Communist Party as saying 19 of those killed were bus passengers. The other two were riding in the coal truck.

The bus was headed to Urumqi, the regional capital, when the accident occurred.

The report quoted police as saying the weather was sunny and had ruled out terrorism as a cause. They suspect fatigue might have played a role.

Xinjiang, China's largest province in size, is on the southern foot of the Tianshan Mountain Range. Poor road conditions in the region are blamed for numerous fatal accidents. In the last such accident on Aug. 12 in Akqi County, 25 people died, the report said.