Libyan military strongman Khalifa Haftar on Wednesday visited a Russian aircraft carrier off the coast of the North African nation in the latest sign of growing relations with Moscow.

The visit comes against a backdrop of rising tensions between Haftar's forces, aligned with an administration based in eastern Libya, and militias loyal to a UN-brokered unity government in Tripoli.

"Marshal Haftar visited the Russian aircraft carrier off (the eastern town of) Tobruk to meet a Russian military delegation," a military source close to Haftar said without giving further details.

Russia's defence ministry confirmed the visit to the Admiral Kuznetsov, which recently completed a two-month mission off Syria supporting President Bashar al-Assad against rebel forces.

It said Haftar met Russian officers and crew before speaking by video link with Russian Defence Minister Sergei Shoigu about counter-terrorism efforts in the Middle East.

The latest sign of closer ties follows a trip by Haftar to Moscow in late November to seek support for an end to the UN arms embargo against Libya.

Haftar's forces, which call themselves the Libyan National Army (LNA), have battled jihadists in second city Benghazi for more than two years and control key eastern oil export terminals.

UN envoy Martin Kobler has expressed alarm about the tensions between the LNA and western militias who support the unity government and who drove Islamic State group jihadists from the city of Sirte in December.

Haftar, accused by his rivals of wanting to install a military regime in Libya, enjoys the support of Arab states including Egypt, the United Arab Emirates and Jordan.