TRIPOLI (Reuters) - Forces loyal to Libya’s internationally recognized government have pushed their eastern opponents back on parts of the frontline south of Tripoli, despite the attackers flying overnight air strikes on the capital, witnesses said on Sunday.

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The Libyan National Army (LNA) force loyal to commander Khalifa Haftar allied to a parallel government in the east started an offensive more two weeks ago but has been unable to breach the southern defenses of the Tripoli government.

The latest flare-up in the cycle of anarchy gripping Libya since dictator Muammar Gaddafi was toppled in 2011 threatens to disrupt oil flows, foment migration across the Mediterranean Sea to Europe, and allow jihadists to exploit the chaos.

Forces loyal to Tripoli managed to push back the LNA several km (miles) in the southern Ain Zara suburb, Reuters reporters visiting the area said. They managed to go several km further south than when they visited the same frontline a few days ago.

Still, if a ceasefire was called as demanded by the United Nations, the LNA would have gained a considerable amount of territory, as they still control much of the area south of Tripoli including a forward base in Gharyan, a mountainous town some 80 km south of Tripoli.

LNA spokesman Ahmed Mismari denied his forces had retreated, telling reporters they had actual gained territory after what he called a successful air strike.

The attackers had late on Saturday flown air strikes on southern areas of Tripoli, with residents blaming drones after listening for almost an hour the typical summing of an unmanned aircraft.

Reuters was unable to confirm whether an aircraft or unmanned drone was behind the strike which triggered heavy anti aircraft fire. Explosions heard in the city center this time were louder than in previous days.

If a drone strike was confirmed this would point to more sophisticated warfare. The LNA has so far mainly used aging Soviet-made jets from the air force of Gaddafi, lacking precision firepower and helicopters, according to residents and military sources.

In the past the United Arab Emirates and Egypt have supported Haftar with air strikes during campaigns to take eastern Libya. Both countries flew air strikes on Tripoli in 2014 during a different conflict to help a Haftar-allied force, U.S. officials said at the time.

Since 2014 the UAE and Egypt have also provided the LNA with military equipment such as aircraft and helicopters, helping Haftar to gain the upper hand in Libya’s eight-year conflict, past U.N. reports have established.

The UAE even built an air base in Al Khadim in eastern Libya, one such report said in 2017.

Fighting over Tripoli spiked after the White House said on Friday that President Donald Trump spoke to Haftar on Monday.

The disclosure of the call and a U.S. statement that it “recognized Field Marshal Haftar’s significant role in fighting terrorism and securing Libya’s oil resources” has boosted the commander’s supporters and enraged his opponents.

Western powers and the Gulf have been divided over a push by Haftar’s forces to seize Tripoli, undermining calls by the United Nations for a ceasefire. On Thursday, both the United States and Russia said they could not support a U.N. Security Council resolution calling for a Libya ceasefire at this time.