Russians on Thursday laid flowers outside the Wagner headquarters in tribute to the mercenary group's chief Yevgeny Prigozhin, who according to Russian officials, was on board a plane that crashed with all passengers killed, months after attempting to topple Moscow's military leadership.

This development comes a day after a private jet on which Prigozhin was registered crashed between Moscow and Saint Petersburg.

Meanwhile, Russia said all ten people onboard were likely killed, and opened a criminal case into violations of air traffic rules.

President Vladimir Putin, who in June faced the biggest challenge in his more than two-decade rule as Prigozhin led an armed mutiny, has not spoken publicly on the crash.

During the rebellion on June 23-24, Putin gave an address to Russians in which he called Prigozhin a "traitor".

But Western leaders reacted, with US President Joe Biden saying "I don't know for a fact what happened. There's not much that happens in Russia that Putin's not behind".