MOSCOW A protest rally in Moscow on Tuesday will test the ability of Russian opposition leaders to maintain pressure on President Vladimir Putin in the face of tough new tactics that show he is determined to quash their challenge to his rule.
Opposition activists vowed to push ahead with plans for the first big rally since Putin's May 7 inauguration, a day after police searched the homes of opposition leaders in raids Kremlin critics said smacked of the era of Soviet dictator Josef Stalin.
Federal investigators summoned prominent opposition leaders to appear for questioning just one hour before the scheduled start of the demonstration.
The moves signaled a harsher approach to dissent at the start of the former KGB officer Putin's new six-year term as president.
On Friday, he signed a law increasing fines, in some cases more than 100-fold, for violations of public order at demonstrations, despite warnings from his human rights council that it was an unconstitutional infringement on free assembly.
Law enforcement officers delivered the summonses during searches of the homes of leaders including anti-corruption blogger Alexei Navalny, leftist firebrand Sergei Udaltsov and socialite Ksenia Sobchak on Monday.
Police and investigators raided their Moscow apartments on a sleepy morning in the middle of a three-day weekend, seizing computer drives and discs, photographs and other belongings as armed guards stood outside.
"People barged in at 8 a.m., gave me no chance to get dressed, robbed the apartment, humiliated me," Sobchak said in a Twitter post. "I never thought we would return to such repression in this country."
"They rifled through everything, every wardrobe, in the toilet, in the refrigerator. They searched under the beds," Udaltsov, who was summoned for questioning along with his wife on Tuesday, told reporters of the search of their home.
Police left Navalny's apartment 13 hours after they entered, carrying boxes. Navalny emerged later and told reporters the summons was clearly aimed to keep him from the rally but vowed that he would attend.
In power since 2000, Putin won a third presidential term in March despite a series of protests that drew tens of thousands into the streets, angry over alleged fraud in a December parliamentary election won by his United Russia party.
Many protesters were middle-class city dwellers who have benefitted from the oil-fuelled boom Russia has experienced during Putin's years at the helm but want more say in politics and fear his prolonged rule will bring economic stagnation.
Police largely left those earlier protests alone but began to crack down after Putin's election, beating protesters at the rally on May 6 and repeatedly dispersing groups trying to set up Occupy-style permanent protests since then, briefly detaining hundreds.
They have detained 12 people over violence at the May 6 protest on charges punishable by more than a year in jail, and the latest summonses seemed to carry the implicit threat that opposition leaders could potentially face similar charges.
Monday's searches sparked a wave of angry comment.
"Vova is crazy," one Twitter user wrote, referring to Putin by the common nickname for Vladimir. Others messaged under the tag that translates as "hello1937" - a reference to the deadliest year of Stalin's repression.
"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 plans for the protest. She said the searches and summonses were clearly a scare tactic.
Udaltsov predicted it would backfire.
"Some people may get scared, but people are less frightened now" following the winter protests, he told reporters. "They are more active, and I think even more people will come than had initially planned to.
"They are digging themselves a pit - deeper and deeper," he said of Putin and United Russia. The party lost dozens of seats in the parliamentary vote, despite allegations of fraud in its favor, but still holds a majority.
Putin used that majority last week to rush the law drastically increasing fines through parliament, a move Kremlin critics said was aimed to suppress dissent.
Under the law, a participant at a gathering at which public order is deemed to have been violated with injury or damage to property can be fined as much as 300,000 roubles ($9,200), about 60 times more than the previous maximum.
Opposition leaders have permission for Tuesday's march and rally in Moscow, but fines can be imposed for minor violations such as blocking traffic, and opposition leaders warned protesters to beware of actions likely to provoke a police response.
(Writing by Steve Gutterman; editing by Andrew Roche)