Fourteen people were killed and 37 others injured after a bus crashed inside an expressway tunnel in northern China, state media reported on Wednesday.

The accident occurred shortly after 2.30pm on Tuesday, broadcaster CCTV reported, citing local authorities in Shanxi province.

The bus, which was carrying 51 people, rammed into the tunnel's interior wall on the Hohhot-Beihai Expressway.

Fourteen people were found dead at the scene, and many others were sent to hospital for treatment, CCTV said.

The cause of the incident is now under investigation. (AFP)