EU alarmed by prospects of battle for Tripoli

The EU did not have any plans to help evacuate European nationals or the UN-backed government from the African metropolis, he said.

"But we are in contact with our delegations there to ensure that the various factions in the conflict try to avoid such things as street fighting," he added.

Borrell spoke after Ghassan Salame, the UN special envoy for Libya, warned at the weekend that a Libyan warlord, Khalifa Haftar, backed by hundreds of Russian mercenaries, could create a "bloodbath" in the city.

The UN and EU-backed Government of National Accord (GNA) in Tripoli also called for Europe's help.

"The public in the city are now asking: 'Why isn't the international community that worked to protect civilians in 2011 doing the same now?'," the GNA's foreign minister, Mohamed Taher Syala, said on Monday, referring to European airstrikes designed to stop a massacre in the Libyan city of Benghazi eight years ago.

"Certainly for Russia, Libya has strategic importance and seeks to have a foothold in the country," Syala also said.

Russia has already expanded its military presence in the Mediterranean after boosting its presence in Syria and selling weapons systems to Turkey.

It has also been accused by Nato generals of "weaponising" migration to Europe, most of which has come via Libya or from Syria, by encouraging people to go to the EU in order to fuel political tensions.

"I fear a bloodbath in Libya, a great migratory movement of people, instability across north Africa taking in the Sahel, and we add to the controversial list of things on which great powers already cannot reach agreement," Salame, the UN special envoy, also said.

For its part, Turkey, another regional power, has so far supported the GNA in Tripoli.

The Turkish president, Recep Tayyip Erdogan, said on Monday that he might send troops there if need be.

"In the event of such a call [a GNA appeal for help] coming, it is Turkey's decision what kind of initiative it will take here. We will not seek the permission of anyone on this," he said.

But its GNA alliance has also caused problems for Europe, after a recent deal to create new maritime boundaries in the Mediterranean in the teeth of Greek and Cypriot claims to maritime zones.

"With this new agreement between Turkey and Libya, we can hold joint exploration operations in these exclusive economic zones that we determined," Erdogan added, referring to an area near the Greek island of Crete.

"Other international actors cannot carry out exploration operations in these areas Turkey drew [up] with this accord without getting permission," he said.

"Greek Cyprus, Egypt, Greece and Israel cannot establish a gas transmission line without first getting permission from Turkey," Erdogan added, amid EU aspirations to build a new gas pipeline through the area, the EastMed pipeline, to reduce energy dependence on Russia.

Erdogan spoke after Greece expelled the Libyan ambassador in protest at the Turkey-Libya maritime pact.

The deal was "problematic" and EU lawyers were examining its legality, Borrell said on Monday.