The United States has accused Russia of deploying jet fighters to Libya in what if confirmed would be a dramatic escalation of its military support for renegade field marshal Khalifa Haftar's war against the country's UN-recognised government.
United States Africa Command said on Tuesday it had monitored several jet fighters flying from Russia to Libya via Syria, and that it expected them to be used to support Russian mercenaries fighting on the ground in support of Gen Haftar's Libyan National Army (LNA).
"We watched as Russia flew fourth generation jet fighters to Libya - every step of the way. Neither the LNA nor private military companies can arm, operate and sustain these fighters without state support - support they are getting from Russia," US Army Gen Stephen Townsend, the head of Africom, said in a statement.
Africom said it had tracked the Russia and that they stopped en-route in Syria, "where it is assessed that they were repainted to camouflage their Russian origin."
It did not say exactly how many aircraft were involved, but released several images of what appeared to be Mig-29 Fulcrum and Su-35 Flanker fighters in flight, as well as one Mig-29 being towed on a runway at the al Jufra airbase 300 miles southeast of Tripoli.
The Russian ministry of defence did not immediately comment on the claims.
The Tripoli-based Government of National Unity last week said it had intelligence that "several" Russian jets had been deployed to the country from Libya, though it was not clear whether they were piloted by Russians.
That claim came as Gen Haftar's Libyan National Army said it was preparing an air campaign in a bid to reverse a series of battlefield setbacks it has suffered over the past month.
Saqr Al-Jaroushi, the head of Gen Haftar's air force, said on May 21 that he was preparing "the largest aerial campaign in Libyan history" and would target Turkish assets that Turkish troops and assets, which have intervened on the side of the GNA.
The GNA has scored a series of victories against the LNA since Turkey has deployed drones, air-defence systems and thousands of ethnically Turkish Syrian fighters at the beginning of the year.
A United Nations report into the war in Libya has concluded that around 1,200 Russian mercenaries have deployed to the country in support of Gen Haftar's troops.
Over the weekend there were reports that several hundred Russian fighters had been flown out of Bani Walid, a town held by Gen Haftar's forces, after pulling out of the frontline near Tripoli.
Sergei Lavrov, the Russian foreign minister, on Tuesday called for a ceasefire and peace talks during a telephone conversation with Aguila Saleh, the speaker of the House of Representatives, a parliament that split from the GNA in 2016. The HoR is based in Tobruk, a city controlled by Gen Haftar.