An explosion caused by a gas leak at a coal mine in eastern Iran has killed at least 51 people and injured more than 20 others.

The blast in South Khorasan province was reportedly caused by a methane gas explosion in two blocks of the mine in Tabas.

South Khorasan's governor, JAVAD GHE-NAAT-ZA-DEH said there were 69 workers in the blocks at the time of the explosion.

It remains unclear how many people are still alive and trapped inside the mine.