The council voted unanimously to extend the work of Operation Sophia until June 2020. It was meeting more than two months after the forces of Khalifa Haftar launched an offensive to seize Tripoli, seat of the UN-recognized government.

Germany told the council that arms supplies delivered in violation of a UN embargo were the main obstacle to ending the fighting in Tripoli and resuming political talks.

"A seemingly unlimited arms supply fuels the erroneous belief in the military solution to the conflict and contributes to the unwillingness of actors on the ground to agree on a ceasefire and resume a political process," said Germany's Deputy UN Ambassador Juergen Schulz.

"It is time to redouble our efforts, to assume our responsibility and ... find ways to finally implement the arms embargo effectively," he told the council.

France said upholding the embargo was a priority "now more than ever," while Britain warned that the weapons flow is harming prospects for a ceasefire.

Belgium and South Africa expressed similar concerns.

The UN resolution allows EU vessels to inspect ships in the Mediterranean suspected of carrying weapons.

The EU, however, suspended naval patrols in March -- a month before Haftar's offensive -- leaving it to air missions to keep track of suspicious ships.

EU foreign policy chief Federica Mogherini has urged European countries to send warships back to the Mediterranean to help enforce the embargo.

UN envoy Ghassan Salame last month called for immediate steps to cut off arms flows to Libya, warning that without quick action, the country would descend into a civil war that could lead to its partition.

In a report to the council, UN sanctions experts said that missiles fired at pro-Tripoli forces in April pointed to a likely drone attack that could involve a "third party," possibly the United Arab Emirates, which has backed Haftar.

Hundreds of people have died and tens of thousands have been displaced in the offensive on Tripoli, while diplomatic efforts to resume political talks have remained deadlocked.