Two people familiar with the matter spoke to The Associated Press, citing US and Ukrainian intelligence assessments.

It’s not clear whether Surovikin faces any charges or where he is being held, reflecting the opaque world of the Kremlin’s politics and uncertainty after the revolt.

But his reported detention comes days after Wagner Group mercenaries took over the military headquarters in the Russian city of Rostov-on-Don and were heading toward Moscow in what appears to have been an aborted insurrection.

Wagner head Yevgeny Prigozhin has spoken positively of Surovikin while criticising the country’s military brass and suggested that he should be appointed the General Staff chief to replace General Valery Gerasimov.

The New York Times this week reported that US officials believe Surovikin had advance knowledge of Prigozhin’s plan to stage the revolt.

The White House and the Kremlin declined to comment.

Surovikin, who has longtime links to Prigozhin, hasn’t been seen since the start of the rebellion when he posted a video urging an end to it.

A Russian military blogger, the Moscow Times, and the Financial Times reported that Surovikin, who is also the commander of the Russian air force, has been arrested.

There has been intense speculation that some top military officers may have colluded with Prigozhin and may now face punishment for the mutiny that briefly sent a virtually unchallenged march toward Moscow that Putin has labeled treason and a “stab in the back”.

Alexei Venediktov, former head of the Ekho Moskvy, a prominent independent radio station that was shut down by authorities after Moscow invaded Ukraine, said Surovikin and his close lieutenants haven’t been in contact with their families for three days, but stopped short of saying that he was detained.

Another prominent military messaging channel, Rybar, which is run by a former defence ministry press officer, reported a purge in the ranks was underway as authorities looked into allegations that some could have sided with Prigozhin.

Surovikin has been linked to Prigozhin since when both were active in Syria, where Russia has waged a military action since 2015 to shore up Syrian President Bashar Assad’s government and to help him reclaim territory after a devastating civil war.

Gerasimov’s own fate also is unclear after the abortive mutiny. While Shoigu showed up at several events attended by Putin, Gerasimov was mysteriously absent.

If a purge is indeed underway, it could destabilise the military chain of command and erode troop morale amid the early stage of Ukraine’s latest counteroffensive and offer Kyiv a chance to reclaim more ground.