The only functioning airport in Libya's capital resumed flights hours after they were suspended on Wednesday following a rocket attack, despite a tenuous truce that world powers pushed warring parties to respect.

Government of National Accord (GNA) forces spokesman Mohammed Gnunu called the rocket barrage a "flagrant threat" to the safety of air traffic at the airport, nine days after it reopened, and a "new violation" of the fragile ceasefire.

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There were no immediate reports of damage or casualties after the rocket fire.

The resumption of shelling on Mitiga International Airport put the truce brokered earlier this month by Russia and Turkey on shaky ground, as diplomatic efforts to halt the long-running civil war intensify.

It was not immediately clear who launched the attack, but suspicion fell on renegade military commander Khalifa Haftar's eastern-based forces, which have been laying siege to Tripoli for months in a bid to wrest authority from the United Nations-recognised government.

Haftar's offensive on the capital has threatened to plunge Libya into chaos rivalling the 2011 conflict that removed and killed longtime leader Muammar Gaddafi.

Despite repeated appeals from UN envoy Ghassan Salame, Mitiga has been the target of several air raids and rocket attacks since Haftar's forces launched their offensive last April.

Haftar's forces, which accuse the GNA of using Mitiga for military purposes, say they target "Turkish drones" being launched from the airport to attack their troops in southern Tripoli.

The GNA has denied the accusations.

On Sunday, world powers with interests in the conflict convened at a peace summit in Berlin, where they pledged to halt foreign interference, honour a widely violated arms embargo, and support a UN-facilitated political process.