An explosion in a coal mine in east Ukraine killed 33 miners, Reuters reported.

The explosion, believed to be a methane gas explosion, happened at the Zasyadko Mine in the city of Donetsk which is being held by Moscow-backed rebels.

Reports of the explosion were followed closely by reports that the rebels held up the rescue effort by restricting access to the mine site.
The Donetsk regional administration said 16 injured people were in hospital.

Earlier in the day, after the body of one miner had been retrieved, the emergency services said 32 people remained trapped in the mine. But hour after hour the death toll kept rising.

"The total deaths amount to 33 people," Interfax news agency reported, citing the region administration's press service.

Donetsk has been the scene of heavy fighting between Moscow-backed separatist rebels, who control the area, and forces loyal to the government in Kiev. A ceasefire has sharply reduced the violence in the past week.

The neighborhood around the mine has come under artillery fire, with fragments from Grad rockets visible on surrounding roads, but mine officials said the explosion was unrelated to the fighting and most likely caused by gas.

In Kiev, Ukrainian Prime Minister Arseny Yatseniuk said rescue workers had been dispatched by the central authorities, "but the Russian terrorists did not let them reach the scene of the accident," he said, using a term commonly used by Kiev to describe the separatists.

The mine, now owned by a private firm, has a history of fatal accidents in the 57 years it has been operating. An explosion at Zasyadko in 2007 killed 106 people. A cemetery next to the pit holds the graves of many miners killed in the past.

The Zasyadko coal mine produced 1.4 Mt (1.5 million st) of coal in 2013. The mine is in the center of a Donbass region which is Ukraine's industrial and coal-producing heartland.

Ukrainian coal production fell 22 percent in 2014 to 65 Mt (72 million st) as the conflict disrupted mining operations, leading to some shortages of coal at power plants.