A group of Russian militants who fight on the Ukrainian side called on the Wagner Group of mercenaries to switch sides and join their ranks to revenge the deaths of Wagner founder Yevgeny Prigozhin and their commander Dmitry Utkin.

Russian air authorities have said Prigozhin, Utkin and eight other people were on a private plane that crashed with no survivors north of Moscow on Wednesday.

"You are facing a serious choice now - you can stand in a stall of Russia's defence ministry and serve as watchdogs for executors of your commanders or take revenge," commander of the Russian Volunteer Corps (RVC) Denis Kapustin said in a video address published late on Thursday.

"To take revenge you need to switch to Ukraine's side," the commander said.

The crash came two months to the day after Prigozhin and his Wagner mercenaries staged a mutiny against Russian military commanders in which they took control of a southern city, Rostov, and advanced towards Moscow before turning around 200 kilometers far from the capital.

Russia has opened an investigation into the crash, but its outcome is unlikely to shake a widespread belief that Prigozhin was killed as an act of vengeance for staging the mutiny.

Reuters had cited two U.S. officials earlier on Thursday saying a surface-to-air missile likely hit the plane. Pentagon later said it had no evidence to support that.

After 24 hours of silence, Russian President Validimir Putin paid "sincere condolences" to the families of all 10 people on the plane, and praised Prigozhin as a "talented businessman".

RVC commander Kapustin, a far-right Russian national, founded the armed group a year ago. RVC fights on the Ukrainian side and has said it was behind several military attacks on Russian border regions.

"Let's end the bloody meat grinder of the special military operation," Kapustin said in his address to Wagner fighters using the Russian official name for the invasion of Ukraine.

"After that, we will march to Moscow and this time we will not stop 200 kilometers before the Moscow ring road but go to the end," he said.