In a major attack ahead of the Lok Sabha polls, Four Border Security Force (BSF) personnel were killed and two injured in an encounter with Naxals in Chhattisgarh Thursday, police said.

As per the Chhattisgarh Police, the encounter took place when a joint team of BSF's 114th battalion and the District Force was out on a search operation in a dense forest near Mahla village at around noon.

Deputy Inspector General (anti-Naxal operations) Sundarraj P said the team had begun the operation from the BSF's Mahla camp, which is located around 250 from Raipur.

He added that the gun battle began as a group of Naxals fired at the security men, who were moving forward through a forest patch.