Alexei Navalny was about to be freed in a prisoner swap when he died, according to his ally Maria Pevchikh.
She said the Russian opposition leader was going to be exchanged for Vadim Krasikov, a Russian hitman who is serving a life sentence for murder in Germany.
Two US citizens currently held in Russia were also going to be part of the deal, Ms Pevchikh claimed.
She added that negotiations were at their final stage on 15 February.
The next day, Mr Navalny died in his cell in the prison colony in Siberia where he was being held on a 19-year sentence over charges that were widely seen as politically motivated. Prison officials said the 47-year-old had fallen ill following a “walk”.
In a video posted on Mr Navalny’s YouTube channel, Ms Pevchikh, who is the chairwoman of his Anti-Corruption Foundation (FBK), said negotiations for a prisoner swap had been under way for two years.
She added that after the start of Russia’s full-scale invasion of Ukraine in February 2022 “it was clear that Putin would stop at nothing” and that Mr Navalny “had to be freed from jail at any cost, and urgently”.
According to Ms Pevchik, Mr Navalny was going to be freed under a humanitarian exchange and American and German officials were involved in the talks.
The process finally resulted in a concrete plan for a prisoner swap in December, she said.
Vadim Krasikov – a Russian who was found guilty of shooting former Chechen rebel commander Zelimkhan Khangoshvili in the head at close range in Germany in 2019 – was going to be part of the deal.
Two US nationals currently held in Russia were also going to be exchanged, Ms Pevchikh said, although she did not name them.
According to Ms Pevchikh, Russian President Vladimir Putin changed his mind at the last minute. She said he “could not tolerate Navalny being free” – and since there was an agreement “in principle” for Krasikov’s freeing, Mr Putin decided to “just get rid of the bargaining chip”.
“Putin has gone mad with hatred for Navalny,” Ms Pevchikh said. “He knows Navalny could’ve defeated him.”
A spokesperson for the German government said on Monday that the government “cannot comment on the reports” of a planned prisoner swap at this time.
Within an hour of publication, Ms Pevchikh’s video had had hundreds of thousands of views.
The Kremlin has not yet reacted to the claims put forward by Ms Pevchikh, but President Putin’s spokesman Dmitry Peskov has previously said allegations of government involvement into Navalny’s death were “absurd”.