ISLAMABAD, Aug. 23 (Xinhua) -- A security official was killed and six others injured when a roadside bomb struck security vehicles in Pakistan's southwest Balochistan province on Saturday, police said.

The explosion occurred in Khad Kocha area of Mastung district along the Quetta-Karachi National Highway, when an explosive device planted near the road was detonated as a security convoy passed through the area, police officials said.

One vehicle was hit in the blast, while other vehicles remained safe, according to a police statement.

An exchange of fire followed the explosion, but the attackers fled before additional security personnel arrived at the scene, the statement said.

The body of the deceased and the injured were shifted to a nearby hospital.

Authorities temporarily closed the highway and launched a search operation to trace those involved in the attack.