The attack occurred in the Bekirhan area of Batman province on Wednesday night where a private oil company operates, Anatolia said.

"Three employees of the firm were killed in the attack which (we) consider the separatist terror organisation committed," Batman governor's office said in a statement carried by Anatolia, referring to the Kurdistan Workers' Party (PKK).

Two of the victims were security guards and the third was a driver, it said, adding that one other employee was slightly injured.

Listed as a terrorist organisation by Turkey and much of the international community, the PKK took up arms for Kurdish independence in southeastern Turkey in 1984, sparking a conflict that has claimed some 45,000 lives.