The Reuters news agency reports that Russia appears to have deployed special forces to an air base near the Libyan border in Egypt.
The report on March 14 cited unnamed sources, including U.S. and Egyptian officials.
Reuters cited U.S. and other sources as saying such a deployment could be part of an effort to support Libyan military commander Khalifa Haftar, who is opposed to the country's UN-backed government.
U.S. officials told Reuters that the United States has seen what appeared to be Russian special forces and drones at Sidi Barrani, Egypt, about 100 kilometers from the Libya border.
Asked about the report, Russian Defense Ministry spokesman Igor Konashenkov said: "There are no Russian special forces units in Sidi Barrani."
Russian President Vladimnir Putin's spokesman, Dmity Peskov, said: "We do not have such information."
Reuters reported that Egyptian security sources described a 22-member Russian special forces unit, but declined to describe its mission, and said that Russia also used an Egyptian base further from the border in early February.
Egypt has denied the presence of any Russian forces on its territory.
Russian Foreign Minister Sergei Lavrov pledged this month to help unify Libya, which was a longtime Soviet client and had close ties to Moscow before the death of dictator Muammar Qaddafi.
Asked on March 14 whether Russia is placing its bets in Libya on Haftar, Peskov said that "any excessive interference by Russia in Libyan affairs would hardly be possible and hardly be expedient."
"But nonetheless, that does not mean that Russia is not making contact with the sides with which it considers it necessary [to do so]."
With reporting by Reuters and Interfax