Russia braced on Saturday for the first nationwide protest of strongman Vladimir Putin's 12-year rule amid signs of swelling anger over a poll won by his party with the alleged help of widescale fraud.
Moscow authorities gave permission for 30,000 people to gather on a square across the river from the Kremlin at 2:00 pm (1000 GMT) after detaining some 1,600 activists who joined unsanctioned rallies against the December 4 vote.
But the opposition is also organising rallies in at least 14 other major cities in a rare outpouring of mistrust in a system put in place by Putin when he first became president in 2000.
A 30,000-strong demonstration would be the largest to hit Moscow since the turbulent late 1990s and ring what some see as the first warning bell for the ex-foreign agent and his secretive inner circle of security chiefs.
Putin's United Russia -- bruised by corruption allegations and comparisons to the Soviet-era Communist Party -- lost its grip on parliament while keeping a slim majority that its foes claim was exaggerated by a corrupt vote count.
Their complaints were supported by a flood of video footage shot by ordinary Russians and posted on the Internet appearing to show ballot stuffing and other widespread manipulation.
The legislative poll was seen as a litmus test of Putin's decision to return to the Kremlin in a March 2012 ballot and appeared to expose a chink in his armour after more than a decade of dominant rule.
Putin accepted the vote's outcome but stayed silent about the protests for three days before accusing US secretary of state Hillary Clinton of inciting the unrest by questioning the polls.
He said Clinton's criticism "had set the tone for some people inside the country and given a signal". US State Department spokesman Mark Toner retorted that "nothing could be further from the truth".
Putin has remained Russia's most popular and powerful politician as both president until 2008 and prime minister today -- an image he cultivated with tough talk against foreign powers and warm words for the Soviet past.
But analysts say rapid social changes and the Internet's first significant gains in Russia may have caught Kremlin strategists off guard amid signs that Putin's likely return is less welcome than originally thought.
A running public opinion poll conducted by the respected Levada Centre show Putin's ratings taking a dive immediately after his planned return to the Kremlin was announced on September 24.
The 59-year-old now finds himself not only exchanging barbs with Washington but also facing a public support dilemma he has never before encountered while in power.
Analysts believe that Putin now has the choice of either embracing reform or tightening state control to preserve to preserve his dominance.
Putin's tirade against the United States would initially suggest the latter. But other signs are less clear.
The authorities' decision to permit Saturday's rallies to go ahead nationwide is a first for the Putin era and suggests the Kremlin would prefer to avoid street battles between protesters and the riot police.
But prosecutors have also launched a probe into a popular Russian social network that was used by the opposition to organise its protests.