The UN Support Mission in Libya called for an immediate halt to the offensive announced by controversial army chief Khalifa Haftar yesterday to give peace talks between the country's rival parliaments a chance.
UNSMIL said it "strongly condemns the military escalation in Benghazi".
"The air strikes are a clear attempt to undermine and derail the ongoing efforts to end the conflict at a time when the negotiations have entered a final and most critical stage," it said.
The country has had rival administrations since August last year when a militia alliance overran the capital forcing the recognised government to seek refuge in the east.
UN envoy Bernardino Leon has expressed hope that the rival sides will finally sign a deal in the Morocco seaside resort of Skhirat later today after months of rejected proposals.
UNSMIL called an "immediate cessation of hostilities in Benghazi and across Libya... To give the ongoing dialogue in Skhirat the chance to successfully conclude in the coming hours.