The death toll rose to 23 on Sunday from clashes between two rival militias in the Libyan capital, according to authorities.
The Libyan Health Ministry said 140 people were also injured in clashes that erupted in several areas in Tripoli.
"Hospitals and health centers affiliated to the Health Ministry in Tripoli have been targeted and bombed since the early hours of the morning," it said in a separate statement.
It urged conflicting parties to protect health institutions, emergency centers, and ambulances in the city from the armed conflict as the fighting intensified.
"The Secretary-General calls for an immediate cessation of violence in Tripoli, Stéphane Dujarric," a Spokesman for the UN Secretary-General said in a statement.
He urges the Libyan parties to engage in a genuine dialogue to address the ongoing political impasse and not to use force to resolve their differences, he said.
He further calls on the parties to protect civilians and refrain from taking any actions that could escalate tensions and deepen divisions, the Spokesman for the UN chief added.
RHM/PR