Maxim Shipenkov / EPA

Masked investigators carry confiscated documents and equipment from the apartment building in which opposition leader Alexei Navalny resides after they finished a raid of his flat in Moscow.

Russian police raided opposition leaders' homes on Monday and summoned them for questioning, disrupting plans for a protest against President Vladimir Putin and suggesting he has lost patience with unrest.

The early morning searches ahead of Tuesday's planned rally were an aggressive turn after months of opposition demonstrations, signaling a tougher approach to dissent at the start of the former KGB spy's new six-year term as president.

Several leaders were ordered to appear for questioning on Tuesday about violence at a rally on the eve of Putin's May 7 inauguration, almost certainly stopping them from attending the first big planned protest since he returned to the Kremlin.

Armed police stood guard as investigators searched the apartments of anti-corruption blogger Alexei Navalny, leftist leader Sergei Udaltsov, socialite and TV personality Ksenia Sobchak and other opposition figures, rifling through rooms and seizing computer drives and discs, photographs and cash.

"They practically cut out the door," Navalny, one organizer of a wave of protests sparked by allegations of fraud in a December parliamentary election won by Putin's United Russia party, said on Twitter. He tweeted that police had confiscated electronics "including discs with the children's photos."

Family members were also targeted by investigators, who searched the homes of Udaltsov's parents and Navalny's in-laws, among others, The Moscow Times reported.

After tolerating the biggest opposition protests of his 12-year rule while seeking election, Putin now looks intent on damping down unrest.

Denis Sinyakov / Reuters

Russian security forces stand guard as an opposition supporter and Anna Veduta, spokeswoman for anti-corruption blogger and opposition activist Alexei Navalny, wait outside the entrance to the apartment block where Navalny lives in Moscow.

On Friday he signed a law that increased fines, in some cases more than 100-fold, for violations of public order at gatherings including street demonstrations, ignoring warnings from his human rights council that it was unconstitutional.

The Investigative Committee, Russia's main investigation agency, said officers had seized "a large quantity of propaganda material and literature with anti-state slogans, electronic databases and computers containing information relevant to the criminal case" opened over violence at the May 6 protest.

At least 1 million euros worth of cash stuffed in dozens of envelopes were also seized in Sobchak’s apartment, The Moscow Times reported.

Investigators vowed to determine the source and purpose for the money.

“My yearly income is more than 2 million. Don't I have the right to keep it at home if I don't trust banks?” Sobchak wrote on Twitter, according to The Moscow Times.

"What we are witnessing today is in essence the year 1937," opposition activist Yevgenia Chirikova said at an emergency meeting in a cramped office to discuss the protest on Tuesday, in reference to the deadliest year of dictator Josef Stalin's repression.

Investigators said the searches were lawful, as part of a probe into a criminal case against activists accused of attacking riot police at a May 6 rally.

Tuesday's "March of Millions” is scheduled to begin at 1 p.m.

Reuters contributed to this report.

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