The Pakistani police said that militants stormed a natural gas and oil extraction plant in northwest Pakistan on Tuesday, killing four police and two private guards.
The attack by up to 50 militants took place at a plant run by the MOL Pakistan Oil and Gas Company in Hangu district near the Afghan border, said police official Irfan Khan.
No group has claimed responsibility.
The company did not immediately respond to an emailed request for comment.
Various militant factions, including the Pakistani Taliban, have operated out of remote mountains in the northwest for years, launching attacks on the security forces and infrastructure in their campaign against the state