MOSCOW - Around 50,000 people rallied in central Moscow Saturday in protest at Russia's intervention in Ukraine, a day before the Crimean peninsula votes on switching to Kremlin rule.
Waving both Ukrainian and Russian flags and shouting slogans heard during the anti-government protests in Kiev, the demonstrators urged Russian President Vladimir Putin to pull troops back from a Cold War-style confrontation.
Marchers carried placards reading "Putin, get out of Ukraine" and others comparing Russia's move on Crimea with the Nazi annexation of the Sudetenland as Europe rushed headlong into World War II.
Many of the protesters adopted the chants and slogans of Ukraine's popular uprising that ousted President Viktor Yanukovych last month.
University professor Yelena Orlova, 47, whose sign read "Ukraine is a sovereign state", said she did not expect the rally would change her government's position, but believed it was her duty to speak out.
"I don't agree with the policy of Putin," she told AFP. "I am against the annexation of Crimea. I think Russia should respect the borders of Ukraine." A huge column of people snaked along a central boulevard with a hotch-potch of flags and hand-written placards.
After the march, the protesters gathered on Prospekt Sakharova, the scene of huge anti-Putin rallies that shook Russia in 2011-12.
"We are patriots and Putin is Russia's enemy," activist Ilya Yashin said from the stage.
"Ukraine is a brotherly nation and we will not allow them (the government) to march us into a fratricidal war." An AFP team at the rally said its numbers had swelled rapidly from an initial 5,000 at around 2.00pm (1000 GMT), and stood at approximately 50,000 two hours later.
An earlier estimate from the police put the number at 3,000.
Russian police frequently downplay the size of opposition demonstrations.
A livestream of the rally on one website accessible in Moscow had been viewed around 240,000 times, according to a counter.
Some leftist protesters were waving the black and red banners of the hugely controversial Ukrainian Insurgent Army (UPA), which fought both Soviet and Nazi forces during World War II.
A helicopter buzzed overhead as some chanted "The main enemy is in the Kremlin. No to fascism, no to imperialism." Days after Europe-leaning activists toppled the Moscow-approved government in Kiev last month, thousands of pro-Russian gunmen took control of Crimea, home to Russia's Black Sea fleet.
A newly appointed government there declared it would leave Ukraine and has set a referendum on the issue for Sunday.
Moscow, which backs the government in Crimea and refuses to recognise the new administration in Kiev, says the plebiscite is a legitimate opportunity for the largely Russian-speaking peninsula to determine its own future.
Kiev and its Western allies say the referendum is an illegal fig leaf for a land-grab by the Kremlin, which it accuses of trying to unilaterally re-draw the post WWII map of Europe.
A rival demonstration within sight of the Kremlin in central Moscow, which appeared to be well-organised, attracted 15,000 people in support of Putin, police estimated.
Television cameras, which swooped over the heads of demonstrators, showed uniform lines of people wearing red and carrying red flags as speakers lashed out at "fascists" in Ukraine they say are targeting ethnic Russians.
"There will never be a Maidan in Moscow," ultra-conservative figure Sergei Kurginyan shouted from the stage, referring to the focal point of the Kiev uprising.