The U.S. military has accused Russia of sending fighter jets to Libya to support Russian mercenaries there, the BBC reports.
There was no immediate response from the Russian Defence Ministry to the U.S. Africa command (Africom) allegation.
Earlier this month a leaked UN report spoke of hundreds of mercenaries from the shadowy Wagner Group operating in Libya. Russia backs renegade Gen Khalifa Haftar's army.
The country has issued a new call for a Libya ceasefire and political talks.
Russian Foreign Minister Sergei Lavrov discussed the conflict with an ally of Gen Haftar by phone on Tuesday, the foreign ministry said.
He told Aguila Saleh Issa, a parliament speaker, that "there needs to be a constructive dialogue involving all the Libyan political forces" and "an immediate ceasefire".
Russia has not confirmed the presence of Wagner mercenaries in Libya. There have been many reports - though not from Russian officials - about Wagner deployments in Syria, eastern Ukraine and other hotspots, including the Central African Republic.
The Russian government denies any state involvement in the militant group.
On 18 May forces of the UN-recognised Tripoli government, fighting Gen Haftar's army, were photographed at a captured airbase, al-Watiya, just south of the Libyan capital.
According to the UN-recognised Government of National Accord (GNA), more than 1,000 Wagner fighters fled an area south of Tripoli aboard Russian transport planes, having been pushed back by GNA troops.
