Vladimir Putin raids campaign offices of Russia’s Anti-Corruption Fund
Navalny said he was detained as he was leaving his Moscow home to go jogging and buy flowers for his wife on her birthday AFP

Russian police on Friday extended a crackdown on the opposition by raiding the offices of independent politicians on the eve of a high-profile protest rally.

On Friday evening, allies of President Vladimir Putin's top opponent Alexei Navalny said police had searched their campaign headquarters.

The latest raids come as opposition politicians prepare to stage an unauthorised rally outside the mayor's offices on Saturday, incensed by officials' refusal to allow them to take part in local elections in September.

"The Investigative Committee has come to the Anti-Corruption Fund," Navalny's ally Ivan Zhdanov said on Twitter, posting a picture of a police bus parked on a street.

Opposition politician and disqualified candidate Ilya Yashin also said police had arrived to search his campaign HQ.

"This is brazen and unlawful pressure on the opposition in the midst of an election campaign," he said on Twitter.

Another would-be candidate Konstantin Yankauskas said police and investigators attempted to search his parents' apartment.

This week authorities launched a clampdown on the opposition as independent politicians are fighting to get on the ballot for a Moscow parliament election.

On Wednesday, Navalny was sentenced to 30 days in jail for calling an unauthorized rally and Zhdanov and several other politicians had their homes searched in nighttime raids.

Politicians were also summoned to the Investigative Committee which reports directly to Putin.

The raids are linked to a new criminal case into obstructing the work of election officials.

For that offense protest organizers may risk up to five years in prison.

Last weekend, 22,000 opposition supporters turned up for a protest in central Moscow, the largest such demonstration in years.