Russian authorities have ordered the offices of imprisoned opposition leader Alexei Navalny to suspend their activities pending a court ruling on whether they should be outlawed as an extremist group.

The injunction from the Moscow prosecutor’s office is another step in a sweeping crackdown on President Vladimir Putin’s fiercest critic and his organisations.

The prosecutor’s office petitioned a court earlier this month to label Mr Navalny’s Foundation for Fighting Corruption and network of regional offices as extremist groups.

Such a label would outlaw their activities and expose members and supporters to lengthy prison terms, according to human rights advocates. It is a major challenge for Mr Navalny’s embattled team, with its leader in prison and dozens of members under arrest, targeted for raids by law enforcement or facing criminal charges.

The prosecutors also asked a Moscow court to restrict the activities of the foundation by banning it from spreading information in the media, taking part in elections, using banks or organising public events, according to Ivan Pavlov, a lawyer representing the foundation.

The injunction from the prosecutor’s office was posted on social media by Mr Navalny’s allies, who reject the accusations and insist the actions are politically motivated.

“It’s a total travesty of justice and lawlessness once again in Putin’s Russia,” said Navalny associate Lyubov Sobol.

“They’re just screaming here: We’re scared of your activities, we’re scared of your protests, we’re scared of your Smart Voting,” tweeted Ivan Zhdanov, Mr Navalny’s top ally and director of the Foundation for Fighting Corruption.

The Smart Voting project is designed to support candidates who are most likely to beat those from United Russia, the party backed by the Kremlin, in various local elections. That plan was successful in some of last year’s regional balloting.

Mr Navalny’s foundation opened 10 years ago and has targeted high-ranking Russian officials with exposes on corruption, many in the form of colourful and widely watched YouTube videos.

One of the latest postings, which has had 116 million views, alleges that a lavish palace on the Black Sea shore was built for Mr Putin through an elaborate corruption scheme. The Kremlin has denied there are any links to the president.

Mr Navalny also set up a vast network of regional offices in dozens of Russian regions when he was campaigning to run against Mr Putin in the 2018 presidential election. He was eventually barred from running but kept the infrastructure in place.

These regional offices began their own investigations of corruption by local officials and recruited activists, some of whom later ran for office. The regional offices also were instrumental in organising nationwide rallies in support of Mr Navalny this year.

He was arrested in January on his return from Germany, where he had spent five months recovering from a nerve agent poisoning that he blames on the Kremlin — accusations that Russian officials reject.

The arrest triggered protests at the time across Russia that proved to be the biggest show of defiance in years, but they did not stop authorities from putting Mr Navalny on trial for violating terms of a suspended sentence stemming from a 2014 embezzlement conviction widely believed to be politically motivated.

He was ordered to serve two and a half years in prison and was last month transferred to a penal colony notorious for its harsh conditions.

In light of Monday’s injunction, Mr Navalny’s offices posted announcements on social media saying they were suspending their activities.

“It’s foolish to get involved in a battle that can’t be won,” Sergei Boiko, head of Mr Navalny’s office in Siberia’s Novosibirsk, wrote on Facebook.

Mr Navalny’s top strategist and head of the regional network Leonid Volkov told the media that all offices had halted their operations.