TRIPOLI, Jan. 31 (Xinhua) -- Libya's army in the southern city of Brak Al-Shati on Wednesday killed two Islamic State (IS) militants, an army source said.

"Two IS affiliates were killed in clashes with the (army) unit and some residents of the city," Mohamed Magrahi, a member of the army's unit 12, told Xinhua.

A soldier in the unit approached three people shopping at a local convenient store after getting out of a car. When asked for their identifies, they became suspicious and shot and killed the soldier before escaping with their car, Magrahi said.

Another soldier from the unit and some young people from the city fired at the terror suspects and chased them until their car broke down. Two of them were found dead later just outside the city, Magrahi added.

IS affiliates often move around the city's southern outskirts, taking advantage of the rough nature of the desert area, Magrahi said.

In December 2015, pro-government forces allied with the Libyan government expelled the IS fighters from Sirte, some 450 km east of Tripoli. The remnants fled to the southern valleys and mountainous areas.

From time to time, the terrorists set up mobile checkpoints on the roads leading to southern cities and search passing cars in attempt to kidnap soldiers or security personnel.