A gas blast at a mine in rebel-held Donetsk, east Ukraine, is feared to have killed as many as 33 miners, with dozens more believed to still be trapped underground.

With the mine in a conflict zone, the death toll has proved difficult to confirm. This morning the speaker of Ukraine's parliament, Volodymyr Groysmas, said in Kiev: "A tragedy occurred… at the Zasyadko mine. There are dead — at the moment, 32 people." However, he later amended the statement saying that he could only confirm one death and that the fate of a further 32 was unknown.

Local officials at the scene have, however, said that around 30 people have been killed. Vladimir Tsymbalenko, the head of the local mining safety service, told Reuters that: "Rescue workers have not yet come to the place of the explosion, they are removing the poisonous gas and then will go down."

According to the BBC, at the time of the blast at least 230 people were underground, of which 157 were rescued by 9am. This leaves 73 unaccounted for.

President Petro Poroshenko has requested access for rescue teams, amid concern that the rebel authorities may not have sufficient resources to respond effectively.

Local media reports varied. The rebel media outlet DAN News cited city official Ivan Prikhodko as saying: "All I can say at the moment is that 32 people are underground, and one person has died. Until the rescue workers reach them, to say they are dead is at the very least unethical."

Video footage outside the mine shows anxious relatives and crying as they gathered outside the mine waiting for news of loved ones.

While Donetsk has been the scene of intense battles between government and rebel forces, there has been no suggestion that the blast was triggered by the fighting, nor that there have been artillery strikes in the area in recent days.

Safety standards in Ukraine's unprofitable state mines have long been poor and wages for workers low. In 2007 three separate accidents at Zasyadko killed 162 workers, including 101 in one incident. The mine is considered to be particularly dangerous and vulnerable due to high levels of underground methane. In 2000 a blast at Luhansk Barakova mine killed 80.