PRISTINA, Serbia (Reuters) - Ethnic Albanian separatist guerrillas ambushed employees at the vital Belacevac coal mine in Kosovo early on Wednesday, wounding three. It was the latest in a reported series of raids on the open-pit mine, Kosovo‘s major source of fuel for generating electricity, by the Kosovo Liberation Army. The KLA seized the mine last June but Serbian security forces recaptured it in early July. Serbian sources said KLA gunmen ambushed two vehicles carrying workers into Belacevac. A mine engineer was shot in the head, while a pit worker was shot in the chest and another in the leg. They were hospitalised in Pristina, capital of the Albanian-majority province in southern Serbia, but their lives were not in danger. A tenuous ceasefire has prevailed in Kosovo for several weeks. A threat of NATO air strikes forced Belgrade to withdraw most army and military police forces last week in a deal that required the KLA to "exercise restraint". But although war combat has ceased, scattered armed violence persists, almost always at night. Guerrillas grabbed control of Belacevac on June 22 and blocked all coal production there before being turfed out by counter-attacking security forces in early July.