Fighters of the Russian private military firm Wagner Group have reportedly shot down Russian military aircraft during its rebellion.

The US think tank Institute for the Study of War said Wagner forces attacked Russian military planes, resulting in "the deaths of at least 13 pilots and airmen."

Russian President Vladimir Putin on Tuesday acknowledged casualties among Russian pilots.

Some Russian media reported that Wagner fighters shot down an Ilyushin Il-22M airborne command post aircraft, as well as helicopters, resulting in the deaths of pilots and other officers.

Britain's defense ministry said in its update on Thursday that the Il-22M is part of a fleet of aircraft that "have played a key role in orchestrating Russian forces in their war against Ukraine."

The ministry also said, "The loss of this aircraft is likely to have a negative impact on Russian air and land operations."

It added that "In the short term, the psychological shock of losing a large number of aircrew in this manner will almost certainly damage morale within the Russian Aerospace Force."

The ministry said that in the longer term, this could lead to undermining "Russia's ability to command and coordinate its forces."