Russia continues to supply a broad range of arms to Libyan rebels including fighter jets, air defence missiles, land mines, and armoured vehicles through the state-backed mercenary Wagner Group, the US Defense Department said Friday.

The Pentagon released satellite photographs that it said shows Wagner-supplied military equipment "on the front lines" of the Libyan conflict in Sirte.

The photos show Russian cargo aircraft including IL-76s, fighter jets, SA-22 missile launch vehicles, heavy trucks and a mine-resistant armoured vehicle, in Sirte and at the Al-Khadim airfield east of Benghazi, the Pentagon said.

US Africa Command director of operations Major General Bradford Gering said the photographs are evidence that Moscow is building its presence in Libya on the side of eastern Libya strongman Khalifa Haftar, who is fighting to seize power from the UN-recognized Government of National Accord in Tripoli.

"The type and volume of equipment demonstrates an intent toward sustained offensive combat action capabilities, not humanitarian relief, and indicates the Russian Ministry of Defense is supporting these operations," Gering said in a statement.

The Africa Command has documented Russia's provision, through the Wagner Group, of least 14 Mig-29 and Su-24 fighter jets to the Libya conflict.

Last week, Africom accused the group of laying land mines in and around Tripoli.

Washington says Russia's activities violate a UN arms embargo on Libya.

"The Russian Federation continues to violate UN Security Council Resolution UNSCR 1970 by actively providing military equipment and fighters to the front lines of the conflict in Libya," Africom said in the statement.