More than 50 people have been killed and hundreds may be missing in northern China after a reservoir of mining waste collapsed, burying cars and homes under a wall of sludge.

Torrential rain triggered the avalanche of mud and rocks after the holding pond at the Tashan mine in Shanxi province was apparently filled beyond capacity.

Xinhua agency says the torrent was several metres high and destroyed houses and a three story office building in minutes.

It says 56 are dead with another 35 injured.

Heavy rain is hampering rescue efforts by more than 1,100 police, firefighters and villagers who are searching for survivors.