At least 13 workers were killed after an explosion in a coal mine in southwestern China on Tuesday, state media said, in the latest mining accident to hit the country.

Another five miners were still missing in the Anping Coal Mine in Guizhou province, the official Xinhua news agency said, citing a local official.

Thirteen miners escaped the blast but three of those died in hospital, the report said.

An investigation into the cause of the accident is under way.

China's coal mines have a notoriously poor safety record, which the government has repeatedly pledged to address.

In 2010, 2,433 people died in coal mine accidents in China, according to official statistics -- a rate of more than six workers per day.

Labour rights groups, however, say the actual death toll is likely much higher, partly due to under-reporting of accidents as mine bosses seek to limit their economic losses and avoid punishment.