TRIPOLI, Aug. 27 (Xinhua) -- Clashes since Sunday night between forces of Libya's UN-backed government and armed militias in the south of the capital Tripoli have killed one civilian and injured three others, Tripoli Security Directorate said Monday.

The directorate condemned the "indiscriminate shelling of civilians" by the clashes in the region of Al-Khalla, urging civilians in the areas to "take caution."

Meanwhile, the municipal council of the nearby city of Tarhuna, some 90 km southeast of Tripoli, confirmed that government forces were attacked by outlawed armed groups.

The armed groups are "intimidating citizens and damaging their properties," it added.

According to witnesses, heavy gun firing and explosions could still be heard in some parts of the city.

The reasons for the clashes remain unknown, as southern Tripoli has been witnessing tensions and military mobilization between armed groups outside and inside the city over the past few days.

Following the 2011 uprising that toppled former leader Muammar Gaddafi's regime, Libya has been suffering escalating violence and chaos, as well as political division.