A bitter war of words erupted Friday between two leading anti-Kremlin Russian opposition factions over allegations of an attack on a close ally of late dissident figurehead Alexei Navalny.
The exchange of accusations has highlighted the tensions within the Russian opposition as they struggle to unite in the face of President Vladimir Putin's quarter-century rule more than two years into his invasion of Ukraine, following Navalny's death in a Russian Arctic prison earlier this year.
The Anti-Corruption Foundation (FBK), the investigative collective set up by Navalny to battle official graft, on Thursday published a video accusing Leonid Nevzlin, a former executive at ex-oil tycoon Mikhail Khodorkovsky's now defunct oil company, of ordering an attack against Navalny's key aide Leonid Volkov in Lithuania in March.
Volkov was briefly admitted to hospital after he was repeatedly struck with a hammer outside his home in Lithuania's capital Vilnius.
A Belarusian man suspected of organising the attack and the two Polish suspected assailants have since been detained.
Citing purported correspondence between Nevzlin and the alleged middleman, the FBK accused the former of hatching an even more dramatic initial plan of seeking to have Volkov forcibly transported by boat from Lithuania to Russia and handed over to the Russian authorities.
Volkov wrote on his social media channels: "Yes, this is a story from the category 'the world will never be the same again'. Yes, it is hard to believe. But, alas, it is true: Leonid Nevzlin was ready to pay $250,000 to perpetrators who were supposed to make me disabled and hand me over to the FSB" Russian security service.
Writing on Telegram, Nevzlin categorically rejected the allegations, saying legal authorities would confirm their "absurdity" and "complete groundlessness".
He alleged that the FBK's information had been obtained from within Russia and said its recent work was "completely within the framework of the Kremlin's information policy and... the tasks set by the Russian special services."
Khodorkovsky, based in London since his 2013 release from over a decade in jail in Russia, on his social media channels defended Israel-based Nevzlin as "my long-term business partner, comrade and friend".
The former oil magnate also noted that state-run Russian channel RT had last week published similar allegations against Nevzlin in a report that was barely noticed at the time.
The FBK has rejected any suggestion of collusion with RT.
Of the accusations, Khodorkovsky said: "Either this is true and then Leonid Nevzlin has gone crazy. Or this is an FSB provocation and a fake, on which a lot of money was spent."
"I am inclined to choose the second version," he said.
Analysts say the Russian opposition is in urgent need of a new unifying figure after the death of Navalny. Supporters say he was killed on the orders of the Kremlin although this is denied by Moscow.