MOSCOW — The lead lawyer defending the Russian opposition leader Aleksei A. Navalny in an extremism case that could outlaw Mr. Navalny’s opposition movement was arrested on Friday, the latest instance of a remarkable escalation by the Kremlin in its long-running campaign to stifle dissent.
The lawyer, Ivan Pavlov, was detained after Russia’s Federal Security Service, or F.S.B., raided his Moscow hotel room at 6:40 a.m., his colleagues said. He stood accused of disclosing details of a law-enforcement investigation unconnected to Mr. Navalny and faced three months of prison time. Mr. Pavlov’s colleagues said agents also searched their group’s St. Petersburg offices and broke down the apartment door of their technology manager.
Mr. Pavlov, one of Russia’s best-known human rights lawyers, has frequently represented high-profile defendants in cases involving the F.S.B., a successor to the K.G.B. that wields enormous influence in Russia. His arrest shook Russia’s activist community because lawyers have, for the most part, been able to continue to operate even as the authorities have intensified their crackdown on the opposition.
“Ivan’s arrest is connected to his professional activity,” a group of lawyers said in an open letter Friday. “We believe that these actions by law enforcement are aimed exclusively at scaring Ivan and his colleagues in order to force them to reject an active position in defending their clients.”
accused of spying for NATO last year.
Team 29 said that Mr. Pavlov was being investigated for allegedly disclosing classified details of the Safronov case to the news media.
But the raids came just four days after Mr. Pavlov took up the defense of Mr. Navalny, Russia’s most prominent opposition figure. On Monday, Team 29 announced it would be representing Mr. Navalny’s organizations in a lawsuit filed in April by Moscow prosecutors to have the organizations outlawed as extremist groups.
said they were shutting down their nationwide network of 40 regional offices.
The crackdown on dissent has accompanied rising tensions between Russia and the West, leaving regular Russians increasingly isolated from the outside world. In response to the April 15 American sanctions against Russia over hacking and other “harmful foreign activities,” Russia countered by, among other things, prohibiting the U.S. Embassy in Moscow from employing people who are not American citizens.
The U.S. Embassy said on Friday that the move had forced it to lay off three quarters of its consular staff. As a result, the embassy said, it would stop processing nearly all nonimmigrant visa requests in Russia, such as for tourism or work travel.
Ivan Nechepurenko contributed reporting.