MOSCOW -- Tens of thousands of people in Moscow and thousands more in cities across Russia on Saturday demanded an end to Vladimir Putin's rule and a rerun of a parliamentary election in the biggest opposition protests since he rose to power 12 years ago.
Protesters turned out in force from the port of Vladivostok in the east to Kaliningrad in the west, nearly 4,600 miles away.
The biggest protest was in Moscow, where riot police were out in force but just watched as protesters waving flags and shouting "Putin is a thief!" staged the biggest protest since the Soviet Union's collapse in 1991.
The protests showed a groundswell of anger over the Dec. 4 election, which the opposition says was rigged to favor Mr. Putin's United Russia, and discontent with the prime minister three months before he tries to reclaim the presidency at the polls.
"Today 60,000, maybe 100,000 people, have come to this rally," former Prime Minister Mikhail Kasyanov said to a huge crowd at Bolotnaya Square across the Moscow River from the Kremlin.
"This means today is the beginning of the end for these thieving authorities," said Mr. Kasyanov, who leads an opposition movement which was barred from the election.
People of all ages gathered in Moscow, many carrying white carnations as the symbol of their protest.
State-controlled TV gave the nationwide demonstrations unexpected airtime, but there is no indication the opposition is strong enough to push for real change.
Nonetheless, the prime minister seems to be in a weaker position than a week ago, before Russians voted in parliamentary elections.
Mr. Putin's United Party lost a substantial share of its seats, although it retains a majority.
The independent Russian election-observer group Golos said Saturday that "it achieved the majority mandate by falsification," international observers reported widespread irregularities, and the outpouring of Russians publicly denouncing him throughout the country undermines Mr. Putin's carefully nurtured image of a strong and beloved leader.
Mr. Putin, president of Russia from 2000-2008 before stepping aside because of term limits, plans to seek a new term in the Kremlin in the March presidential election. The protests have tarnished his campaign, but no strong challenger has appeared yet.