POLICE armed with assault rifles raided the homes of Russia’s top protest leaders yesterday in a show of force on the eve of a mass Moscow rally against President Vladimir Putin’s rule.

The co-ordinated security sweep in the early hours of a public holiday targeted the homes of a new brand of young Russian politicians who analysts believe represent the biggest threat to ex-KGB spy Putin’s 12-year rule.

Officers beat down the doors of popular anti-corruption blogger Alexei Navalny as well as media celebrity Ksenya Sobchak.

Others on the list included Sergei Udaltsov — an ultra-leftist who stages hunger strikes to protest his repeated arrests — and the more moderate democracy campaigner Ilya Yashin.

“They are taking all the electronic devices,” Mr Navalny tweeted during the raid. “Even disks with photos of the children.”

The Investigative Committee said 10 raids were conducted in all as part of a probe over a previous demonstration “that ended in mass disturbances”.

A march that drew 20,000 people in Moscow on May 6 ended in the arrest of hundreds after clashes broke out between protesters and police on the eve of Mr Putin’s inauguration to a third term.

Mr Navalny and the nine others face up to 10 years in prison if they are charged and convicted of organising mass disturbances.

The May 6 unrest sparked a stiff response from the Kremlin that saw Mr Putin on Friday sign into law legislation dramatically raising fines for those who break the already restrictive laws on organising and holding rallies.

The highest penalty for individuals has been raised to 300,000 rubles ($9000) — more than for any other administrative offence and about equivalent to Russians’ average annual salary.

Rights activists said the security agencies were trying to intimidate the nascent movement and prevent mass attendance in order to avoid embarrassing Mr Putin just a month into his third term.

City authorities have authorised up to 50,000 people to take part in a rally today at the site of a December protest against fraud-tainted parliamentary polls.

But the Investigative Committee ordered all 10 to appear for questioning only hours before the rally was was due to start.

“They are trying to disrupt the ‘March of Millions’ and make sure fewer people come,” activist Lev Ponomaryov told Interfax.

Former finance chief Alexei Kudrin — a friend of Mr Putin who quit last year over after his job swap with Prime Minister Dmitry Medvedev — said the raids showed “radicals gaining strength” in the Kremlin.

He said the raids and stiff new penalties would only energise the protest movement and give it the momentum it appeared to be losing after Mr Putin’s dominant win in March 4 presidential elections.

The protest leaders’ representatives said the searches were unexpected and similar to those conducted in far more serious cases involving grave crimes.

Mr Navalny’s lawyer Olga Mikhailova told Moscow Echo radio that “around 15 policemen burst” into his Moscow apartment yesterday morning and presented him with a search warrant.

“Initially, they tried to break down the door,” she said.

The radio station’s deputy editor reported from Ms Sobchak’s apartment building that armed police were at the entrance and preventing others from getting in.

Mr Udaltsov said police had spent six hours searching through his apartment and left with his computer hard drive and memory devices. “They also searched my parents’ apartment . . . but did not find anything interesting,” he told Interfax.