An explosion triggered by a gas leak at a coal mine in eastern Iran on Sunday left at least 51 people dead, media reports said.

The blast in South Khorasan province left 20 others injured.

Mohammad-Ali Akhondi, the director general of the provincial crisis management department, told IRNA news agency that the accident was caused by a methane gas explosion in two blocks of the mine on Saturday night.

A rescue operation was initiated after the blast occurred.

"The reality is that it is a difficult task to rescue the injured from a depth of 700 meters diagonally and 250 meters vertically underground,” an official told IRNA.

According to reports, 69 labourers were present in the blocks when the blast took place.

President Masoud Pezeshkian has condoled the loss of lives in the incident.

"I offer my condolences from the bottom of my heart to the compatriots who lost their loved ones in this incident, and I consider myself a partner in their grief," he posted on X.

"The Ministers of Labor and Security have been sent to Tabas to investigate and deal with the issue," he said.