The council voted unanimously to extend authorization of Operation Sophia until June 2020, 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 hurdle in the way of an end to the fighting in Tripoli and a return to political talks.

"A seemingly unlimited arms supply fuel 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 responsiblity and ... find ways to finally implement the arms embargo effectively," he told the council.

Belgium also expressed concerns about arms flows as did South Africa.

The resolution, first adopted in 2016, allows vessels of the EU operation to inspect ships in the Mediterranean suspected of carrying weapons.

The EU, however, suspended naval patrols in March, 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, Libya will descend into civil war that could lead to a partition of the country.

UN sanctions experts have said in a report to the council 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.

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