A large number of online attacks have been reported in Russia against websites deemed to be anti-President Putin.
The sites are being crashed or slowed severely by distributed denial-of-service attacks similar to those directed against Estonia earlier in the year.
The outlawed National Bolshevik Party claimed that it had been under attack between February and April when it was trying to organise anti-government protests.
"They killed the entire US server that hosted us," the party's online supervisor Alexei Sochnev told Associated Press.
Meanwhile Pavel Chernikov, owner of news site Kommersant, reported that his site was attacked in early May after publishing a report on Russian exile Boris Berezovsky.
On the same day radio station Ekho Moskvy was taken down by a denial-of-service attack.
"A huge information war awaits Russia before the elections," said Oleg Panfilov of the Center for Journalism in Extreme Situations.
"There will be purges of online publications, shutdowns or takeovers of independent media outlets and strong pressure on web users."
Russian officials have denied any involvement in online attacks against Estonia, suggesting that it would be easy for hackers to fake IP addresses that make it look as though they were from government systems.
Stanislav Belkovsky, from the Moscow-based National Strategy Institute, claimed that the attacks were being orchestrated from within Putin's inner circle in an attempt to crack down on online activities over which the Kremlin has no control.
"The Kremlin cannot just tell their editors to remove an unwanted publication," he said.
The internet is proving to be one of the few ways to get an opposition message out. Opposition leader and former chess champion Gary Kasparov recently joked that YouTube was the only communication tool they had.
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