Jailed Kremlin critic Alexei Navalny says he has been charged in a new criminal case and faces “up to 15 more years” on top of his existing sentence if found guilty.
Mr Navalny has been outspoken against President Vladimir Putin and was sentenced in March to nine years in prison after he was found guilty of large-scale fraud and contempt of court.
Antony Blinken, the US secretary of state, previously described the charges as dubious.
Mr Navalny, 45, wrote about the new allegations on Twitter on Tuesday, saying he had been charged with creating an extremist organisation and inciting hate towards the authorities.
“It turns out that I created an extremist group in order to incite hatred towards officials and oligarchs,” he said.
“And when they put me in jail, I dared to be disgruntled about it (silly me) and called for rallies.
“For that, they’re supposed to add up to 15 more years to my sentence.”
There was no immediate confirmation from authorities of the new charges.
A vocal critic of the Putin regime
Mr Navalny, who was born near Moscow in the then-Soviet Union, has long been Mr Putin’s most vocal critic within Russia.
In June last year, a Russian court banned groups linked to Mr Navalny after declaring them “extremist”.
Mr Navalny is seen on a screen via a video link during an earlier court hearing
Following the invasion of Ukraine, the Kremlin has accelerated its decades-long campaign to quash and silence Russia’s domestic opposition.
Mr Navalny has spoken out against the war, attacking Mr Putin during a court appearance and calling the invasion “stupid” and “built on lies”.
While serving his jail sentence he called on fellow citizens to stage daily protests.
Mr Navalny has been outspoken against President Vladimir Putin
Arrest and imprisonment
He was arrested in January 2021 after returning to Russia from Germany where he had spent time recovering from nerve agent poisoning.
The Russian opposition leader had fallen ill on a flight to Moscow and was subsequently found to have been poisoned with novichock during a campaign trip in Siberia.
Mr Navalny has blamed the poisoning on the Kremlin. Russian authorities have denied involvement.
The Putin critic looks at a camera while speaking via a video link from jail
He was put on trial and sentenced to nine years in prison in March.
After the sentencing, he wrote on Twitter that Mr Putin is “afraid of the truth”.
Concerns have since been raised about Mr Navalny’s health in jail, with reports that prison authorities have refused to give him the right medication and not allowed his doctor to visit him behind bars.