The decision to let up to 30,000 protesters rally on Saturday on a square across the river from the Kremlin appears to be an attempt to avoid the violence that occurred at demonstrations after last Sunday's parliamentary election.
Election authorities on Friday officially declared the vote valid, handing the victory to Prime Minister Vladimir Putin's United Russia party. The party won 49 percent of the vote, but was granted 53 percent seats in the house because of votes redistributed from the three parties that did not meet the 5 percent threshold.
Russia's opposition parties and observers said that even that result was highly inflated because of vote-rigging, and international monitors also pointed to ballot stuffing.
The post-election protests in Moscow drew thousands and continued for several days in the biggest ever challenge to Putin, reflecting growing public frustration with his rule that may complicate his bid to reclaim the presidency in March's vote. The rallies were brutally dispersed by police, who rounded up hundreds of protesters.
The protesters have used the Internet to coordinate their action. Over 30,000 people have already signed up to a Facebook page on Saturday's protest, and similar rallies are also planned in many cities across Russia to demand an investigation into the alleged vote fraud and call for a new vote.
Ilya Ponomaryov, a lawmaker who is one of the leaders of the Left Front opposition movement, described the protest planned for Saturday as a watershed event similar to massive rallies that helped bring down Communist rule two decades ago.
"We expect it to become the biggest political protest in 20 years," he said at a news conference.
Putin served two presidential terms from 2000 until 2008, when he shifted into the prime minister's job to abide by constitutional term limits, but remained the nation's No. 1 leader. Putin's decision to swap seats now with his protege, President Dmitry Medvedev, has angered many Russians, who fear it will further strengthen authoritarian trends in his policy and lead to political and economic stagnation.
Putin still seems all but certain to win the March election, but he clearly has been taken aback by the tide of public anger. On Thursday, he accused U.S. Secretary of State Hillary Clinton of instigating protesters in order to weaken Russia and warned that his government might take an even harder line against those who try to influence Russia's political process on behalf of a foreign government.
Alexander Gorbenko, a deputy mayor of Moscow who has allowed Saturday's protest, sternly warned its participants Friday that any attempt to hold a march after the rally will be stopped by police.
But some of the protest organizers said Friday they will gather in a different location nearer the Kremlin prior to the event, and lead protesters to the square where the authorities have permitted the rally. That raises the possibility of new violence.
Authorities have put nearly 50,000 police and about 2,000 paramilitary forces on the streets, backed by water cannons.
International human rights groups have criticized Russian authorities for the brutal suppression of this week's rallies and urged them to respect the freedom of assembly.
Memorial, a prominent Russian rights group, said in a statement Friday that many of those detained during the rallies were beaten, held in overcrowded cells and denied food. Memorial said dozens have been sentenced to up to 15 days in jail on fabricated charges by courts, which "didn't even bother to create even a semblance of justice."
The Organization for Security and Cooperation in Europe on Friday urged Russian authorities to protect journalists reporting on the protests from detention and police harassment. It said about two dozen reporters covering this week's rallies in Moscow and St. Petersburg were rounded up by police.
"The duty of the police is to protect journalists, not harass and detain them," OSCE Representative on Freedom of the Media Dunja Mijatovic said in a statement. "The Russian authorities should investigate all these incidents and ensure that the perpetrators are swiftly prosecuted."
Associated Press writer Nataliya Vasilyeva contributed to this report.