The tragedy struck Friday afternoon at a mine in Chenzhou city in Hunan province when a detonator and explosives warehouse blew up, an employee at the city's coal industry bureau, who would only give his surname Li, told AFP.

"Up to this morning we have confirmed there are 18 dead and three injured," he said.

Li said the victims were in dormitories next to the warehouse at the time of the explosion.

According to the official Xinhua news agency, a further two people were missing, and police have said the detonators and explosives might have been illegally bought and stored.

China's coal mines are notoriously dangerous. Official figures show that more than 3,200 workers died in collieries last year, but independent observers say the actual figure could be much higher, as many accidents are covered up.