Tens of thousands of people have taken part in the biggest anti-government street demonstrations in Russia in a decade, in protest against alleged fraud in last Sunday's parliamentary elections.
An estimated 50,000 people attended a rally in Moscow demanding that Prime Minister Vladimir Putin step down. Thousands of police and riot troops were deployed in the Russian capital.
Protesters waved banners such as "The rats should go!" and "Swindlers and thieves - give us our elections back!" in cities from the Pacific port of Vladivostok in the east to Kaliningrad in the west, nearly 7,400km away.
Riot police were out in force with dogs and in trucks, but they did little to douse protests that showed a groundswell of discontent with Mr Putin as he prepares to reclaim the presidency next year, and anger over the 4 December election which the opposition says was rigged to favour his United Russia party.
"Today 60,000, maybe 100,000 people, have come to this rally," former prime minister Mikhail Kasyanov said in a speech to flag-waving and chanting protesters packed into 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 now 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 and some waving pictures of Putin and President Dmitry Medvedev declaring: "Guys, it's time to go." Helicopters at times buzzed overhead.
Vladimir Ryzhkov, an opposition leader, read out a list of demands including annulling the election and holding a new one, registering opposition parties, dismissing the election commission head and freeing people the protesters call political prisoners.
"Russia has changed today - the future has changed," he said, urging demonstrators to come out for new protests on 24 Decrmber. The crowd chanted, "We'll be back!"
But Konstantin Kosachyov, a United Russia lawmaker speaking on behalf of the Kremlin, ruled out negotiations on the organisers' demands and said: "With all respect for the people who came out to protest, they are not a political party."
The rallies, many of them held in freezing snow, were a test of the opposition's ability to turn public anger into a mass protest movement on the scale of the Arab Spring rebellions that brought down rulers in the Middle East and North Africa.
Most Russian political experts say the former KGB spy who has dominated the world's largest energy producer for 12 years is in little immediate danger of being toppled and that protests are hard to keep going across such a vast country.
But they say Mr Putin's authority has been badly damaged and may gradually fade away when he returns as president unless he answers demands ranging from holding fair elections to reducing the huge gap between rich and poor.