An explosion in a mine in West Virginia has killed 25 miners and left four others unaccounted for.

The accident at the Upper Big Branch Mine in Montcoal is one of the deadliest at a US coal mine in recent years.

The mine, owned by Massey Energy, is about 48km south of state capital Charleston.

Mine officials said the death toll rose after rescuers discovered more bodies underground hours after the blast.

Kevin Strickland of the US Mine Safety and Health Administration's said four men were still missing.

'This is still a rescue operation,' said Mr Strickland, adding, however, that there was little hope the miners would be found alive.

Mr Strickland said rescue teams have been forced to pull back from the search area because of a continuing threat of methane gas underground.

The rescuers intend to drill a borehole from the surface above the mine to try to reach the missing men.

'We want to assure the families of all the miners we are taking every action possible to locate and rescue those still missing,' said Massey's CEO Don Blankenship.

Rescuers include officials from state and federal mine safety agencies and first responders from all levels of government, said Leslie Fitzwater, a spokeswoman for the West Virginia Department of Commerce.

West Virginia Governor Joe Manchin called the news 'devastating' and offered support to the miners' relatives.

'For those families who are still waiting for news on their missing loved ones, I want them to know that we are doing everything possible in cooperation with federal officials and the company to get our miners out as quickly and safely as possible,' Mr Manchin said on his website.

Mr Manchin said he has spoken with President Barack Obama about the disaster.