Ukrainian President Leonid Kuchma has expressed his condolences to the relatives of the victims.

A government commission headed by Deputy Prime Minister Oleh Dubyna has been set up to investigate the accident.

The Emergency Service Ministry was quoted as saying three other miners had died at three different coal mines on Saturday, all as a result of violating safety rules.

Deadly methane

Naturally occurring gas Seeps out of coal seams Builds up in poorly-ventilated shifts

The death rate in Ukrainian mines is among the highest in the world. At least 300 miners died last year.

That included the country's worst accident, at the Barakova mine, in Krasnodon, when 80 people were killed.

Investment shortages

BBC correspondents say shoddy working practices and low safety standards in Soviet times caused many mishaps.

And since it gained its independence in 1991, Ukraine has been too poor to devote the necessary resources to improving matters.

Ukraine has 400,000 coal workers and more than 200 mines, concentrated in the Donbass coal region in the east of the country.