Russian opposition leader Alexei Navalny and his associates are facing fresh criminal charges.
Authorities in Russia have opened a new investigation against the imprisoned Kremlin critic, accusing him of forming an "extremist" group.
Several of Navalny's top allies, including Leonid Volkov and Lyubov Sobol, are also facing charges for participating in an illegal organisation.
Russia’s Investigative Committee said in a statement that the charges carry a maximum prison sentence of between six and ten years.
The new probe is the latest step in a multi-pronged crackdown on Navalny and his anti-corruption foundation.
"This is the fourth criminal case launched against Alexei while he’s in prison," Navalny’s spokeswoman Kira Yarmysh said on Twitter.
The Investigative Committee alleged that the Foundation for Fighting Corruption was set up to discredit Russian authorities and destabilise the country.
The group is accused of "creating a protest mood among the population and forming public opinion about the need for a violent change of power."
In June, a court in Moscow labeled Navalny’s network an extremist group, a ruling that exposed his associates and supporters to prosecution and potentially lengthy prison terms.
Navalny's associates say they expect the crackdown of their actions to continue for months and years.
Sobol told the Associated Press that the foundation had "never been any kind of extremist" and that the new case against the Navalny team was politically motivated.
"We took part in elections, participated in peaceful protests against injustice, we worked on investigations that received dozens of millions of views on YouTube."
"Our activity has always remained within the law," she added.
Navalny and his allies have faced unprecedented pressure ever since the Kremlin critic returned to Russia in January from Germany, where he spent five months recovering from a nerve agent poisoning.
Navalny blames the poisoning on the Kremlin, an accusation that Moscow has denied.
Navalny was arrested upon landing in Moscow and ordered to serve 2½ years in prison for violating parole from a previous conviction he says is politically motivated.
Before this month's parliamentary elections, Russian officials also blocked nearly 50 websites run by Navalny’s allies and pressured Apple and Google to remove his app from their online stores.
The elections, which critics of the Kremlin say were riddled with fraud, were won by Vladimir Putin's party as he seeks re-election in 2024.