ROME: The United Nations is preparing to deploy up to 250 Nepale guards to Libya to protect its base in the capital as part of a plan to return its operations to the country, the head of the organisation's mission there said on Friday.

Backed by Western governments, the United Nations is trying to heal a rift between Libya's rival factions in order to stabilise the country and to tackle militant violence and people-smuggling from Libya's northern coast.

The mission has been based in Tunis since 2014, when fighting among rival Libyan brigades forced out most foreign embassy staff, but it has gradually increased its presence in Libya and has been planning for months for a fuller return.

The military unit would probably consist of around 150 guards, Jean-Pierre Lacroix, UN Under-Secretary-General for Peacekeeping Operations, told a news briefing in Geneva.

"To make sure that we protect our colleagues as they deploy in Tripoli there will be a guard unit which will be basically UN military personnel coming from Nepal," Lacroix said.

Envoy Ghassan Salame told Italian newspaper La Stampa that "a little under 250" could be deployed in the "coming weeks".

Deploying the guards to the base in Tripoli "will mean that around the beginning of October we can carry out a significant part of our work in Libya," said Salame, who has headed the mission since June.

Security in Tripoli and other parts of western Libya is fragile, and armed groups that are largely unaccountable hold power on the ground.

Most foreign embassies closed and pulled out their staff in 2014 when heavy fighting between rival factions destroyed the capital's airport. It was the worst fighting since the fall of long-time leader Muammar Gaddafi in 2011.

Libya slipped into turmoil after the NATO-backed uprising that toppled Gaddafi. A UN-backed government set up in Tripoli last year has struggled to assert its authority and is opposed by factions that control eastern Libya.

In July, rival leaders pledged to work towards elections in 2018 and a conditional ceasefire. Salame said constitutional and electoral laws would have to be written to ensure any vote brought lasting change.

"We need to be sure everyone accepts the final result," he said. "Let's not forget that presidential elections would be the first ever."