TRIPOLI, April 6 (Xinhua) -- Air force of Libya's UN-backed government on Saturday attacked forces of the eastern-based army in south of the capital Tripoli, as the army continues trying to take over the city.

"Fighter jets took off from Misurata airbase (some 200 km east of Tripoli) and carried out three airstrikes against Haftar's army in two locations in southern Tripoli," a government military source told Xinhua.

The airstrikes targeted gatherings of machinery and equipment of the army, the source said, revealing no details about possible human casualties.

The army, led by General Khalifa Haftar, on Thursday launched an operation to take over Tripoli where the UN-backed government is based.

The army's spokesman, Ahmad al-Mismari, on Friday revealed that the army is making significant progress towards the city, and that areas in southern Tripoli are now under the control of the army.

UN Secretary-General Antonio Guterres, who concluded a visit to Libya on Friday, expressed deep concern over the military escalation in Tripoli.

"I still hope it will be possible to avoid a bloody confrontation in and around Tripoli," Guterres told reporters before departing from the eastern city of Benghazi.

Libya has been struggling to make a democratic transition amid insecurity and chaos, ever since the fall of former leader Gaddafi's regime in 2011.