UN chief Antonio Guterres on Monday appealed for an immediate halt to fighting in Libya, after strongman Khalifa Haftar's forces claimed an airstrike on Tripoli's only functioning airport.
Thousands have fled violence in the capital city, according to the United Nations, since Haftar launched a surprise assault last week which has left dozens dead.
Secretary-General Guterres "urges the immediate halt of all military operations in order to de-escalate the situation and prevent an all-out conflict," said a UN statement late Monday.
He "strongly condemns the military escalation and ongoing fighting in and around Tripoli, including the aerial attack today by a Libyan National Army (LNA) aircraft against Mitiga airport."
The oil-rich northern African country has been rocked by violent power struggles between an array of armed groups since the Nato-backed overthrow of dictator Moamer Gaddafi in 2011.
The UN-backed Government of National Accord (GNA) controls the capital, but its authority is not recognized by a parallel administration in the east of the country, backed by Haftar.
The strongman has defied international calls to halt his advance on Tripoli, including from the UN Security Council and the United States.
"I make a very strong appeal to Libyan leaders and in particular to Haftar to stop all military activities... and to return to the negotiation table", the EU's foreign policy chief Federica Mogherini said after talks with EU foreign ministers.
The GNA said French President Emmanuel Macron spoke with its leader Fayez al-Sarraj of his "total opposition to the offensive against the capital and the endangering of civilian lives".
The French presidency confirmed the call took place, without releasing details of the discussion.