Islamic State militants will "stop at nothing" to strengthen their presence in Libya and the urgency of a request by the country for international help to tackle the extremists should not be underestimated, a top United Nations official said today.

UN special envoy Bernadino Leon briefed the United Nations Security Council on the situation in Libya, where two rival governments and their armed forces are battling for control four years after the civil war that ousted Muammar Gaddafi.

Islamist militants have bolstered their foothold in the North African state amid the chaos and yesterday stormed two oilfields, driving out security forces.

"I have no doubt that terrorists groups, such as Islamic State, will stop at nothing in their bid to play on existing political divisions... to consolidate their own presence and influence in Libya," Leon told the 15-member council.

He said the international community should be ready to support Libyan efforts to tackle terrorism and extremism.

"We should be careful to not underestimate the sense of urgency and alarm underpinning this request for international support on addressing the threat of terrorism," Leon said.

United Nations sanctions monitors said in a new report that Libyan authorities are unable to halt the illicit trade in oil or the flow of weapons and need an international maritime force to help.

Libya, backed by Egypt, has called for the Security Council to lift an arms embargo. The government is already allowed to import weapons with the approval of a Security Council committee overseeing the embargo imposed in 2011.

Libyan U.N. Ambassador Ibrahim Dabbashi said the Libyan army recently made some specific exemption requests to the committee.

"These requests related to reinforcing the abilities of the Libyan air force so that it may be able to monitor Libyan territory and borders and prevent the terrorists from breaching oil fields and oil facilities and so that it can protect the fortunes and the wealth of the country," he said.

Fighting and air strikes have escalated even as the United Nations prepares to restart negotiations this week between the two factions in an attempt to broker a ceasefire, form a unity government and put Libya back on track to stability.

"Unless Libyan leaders act quickly and decisively, the risk of their country's national unity and territorial integrity are real and imminent," Leon said.

Sign up to our free newsletters

Get the best updates straight to your inbox:
Please select at least one mailing list.

You can unsubscribe at any time by clicking the link in the footer of our emails. We use Mailchimp as our marketing platform. By subscribing, you acknowledge that your information will be transferred to Mailchimp for processing.