The UN’s International Organization for Migration (IOM) called “for an immediate cessation of hostilities to ensure the safety and wellbeing of civilians in accordance with International Humanitarian Law”.

Their statement came amid fresh unrest in Libya, which has struggled to recover from the Nato-backed 2011 uprising that toppled and killed longtime leader Moamer Kadhafi.

The country remains split between a UN-recognised government in Tripoli, led by Prime Minister Abdul hamid Dbeibah, and a rival administration in the east, controlled by the Haftar family.

Fresh gun battles erupted Wednesday in the Libyan capital between two powerful armed groups, a security official said, a day after the authorities had declared the fighting over.

On Monday night, heavy arms fire and explosions rocked several Tripoli districts, killing at least six people, said officials.

The official described the fighting as “urban warfare”, with clashes in residential areas involving light and medium weapons. In other areas, heavy weapons were used.

The IOM said it was “alarmed by the recent escalation of violence in Tripoli”.

It added: “We are also concerned by the mobilisation of armed groups in surrounding regions. There is a severe risk of mass displacement and danger to civilians.”

On Tuesday, the Tripoli-based government said the fighting had been controlled and announced a ceasefire, even as shots were still fired in western parts of Tripoli.

“We welcome reports of a ceasefire and urge that it be fully and unconditionally respected to safeguard the rights and dignity of all those in the affected areas,” the IOM said.

“IOM continues working with partners to support humanitarian access to all vulnerable groups, including migrants,” it added.

“We are monitoring possible displacement trends and stand ready to support should needs arise.”