MOSCOW (AFP) - Russian police on Friday were searching the home of opposition leader and President Vladimir Putin's biggest critic Alexei Navalny, his lawyer said.

Investigators, police and agents from the FSB, the successor agency to the Soviet-era KGB, arrived at Navalny's Moscow flat at 4am, his lawyer Vladimir Kobzev wrote on Twitter.

Navalny was convicted of embezzlement in July last year and given a five-year suspended jail sentence. He is currently being tried in another fraud case during which he has been put under house arrest and banned from using the phone or the Internet.

He and his supporters charge that the cases against him are politically motivated.

His colleagues and wife update his website and popular Twitter account and on Friday posted a picture of him, smiling in a T-shirt in his living room as men in civilian clothing looked around and took notes.

Friday's search was tied to yet another probe against him in which he is alleged to have defrauded an opposition party eight years ago.

The charismatic 38-year-old lawyer came in second in last year's election for Moscow mayor, with 27 per cent of the vote.

Russian authorities have not allowed him to register a party and earlier this month charged some of his closest associates with fraud linked to his crowdfunded mayoral campaign.