Beijing  - A gas explosion at a coal mine in north-east China trapped 139 workers early Saturday, local media reported.

More than 500 miners were working when the explosion occurred at 2:30 am in a mine in Hegang City, Heilongjiang province, the state-run Xinhua news agency reported, citing the provincial coal mine safety watchdog.

Local residents in Hegang, 10 kilometres from the mine site, said the had felt the blast, the semi-official China News Service reported.

Rescue operations were underway, Xinhua said, and more than 300 miners had been found. The number of casualties was not known.

China's mining industry is notoriously dangerous with many mines operating illegally and flouting safety regulations in order to increase production.

The official mining death toll was 3,215 last year, but industry analysts suspect the actual figure to be higher. (dpa)