A deadly explosion ripped through the Luhansk regional administration building in that city -- which has been occupied by the "Luhansk People's Republic," but the cause was disputed.

The pro-Russia separatists who seized the building several weeks ago claimed an air strike hit their headquarters on June 2, killing at least five people and injuring 10, UNIAN reports.

A local health official said at least two people had been killed.

A Defense Ministry spokesman said the blast was most likely caused by careless handling of explosives.

A witness was quoted as saying the explosion was probably caused by a missile fired from another separatist-occupied building.

There has been fighting in Luhansk since the early hours of June 2, when in a separate incident separatists tried to storm the local headquarters of the Ukrainian border guards.

Russia's Foreign Ministry has issued a statement accusing the government in Kyiv of committing "another crime against its own people" in connection with the event.

Photo: RIA Novosti