WASHINGTON (AFP) - The United States criticised Moscow for arresting hundreds of people demonstrating against corruption, calling the move an "affront" to democracy.
The march in Moscow on Sunday (March 26) was one of the biggest unauthorised demonstrations in recent years. Police put the turnout at 7,000 to 8,000 people.
"The United States strongly condemns the detention of hundreds of peaceful protesters throughout Russia," acting State Department spokesman Mark Toner said in a statement.
"Detaining peaceful protesters, human rights observers, and journalists is an affront to core democratic values."
Among those arrested was opposition leader Alexei Navalny, whose anti-corruption foundation organised the marches.
Mr Toner said the United States was "troubled" by the arrest of Navalny, who has announced plans to run for president in the 2018 election and published a detailed report this month accusing Prime Minister Dmitry Medvedev of controlling a property empire through a shadowy network of non-profit organisations.
Police said about 500 people had been arrested in Moscow, while OVD-Info, a website that monitors the detention of activists, said at least 933 had been detained, as well as dozens in other cities.
Russia's Interfax news agency said 130 people were arrested in Saint Petersburg, where about 4,000 people gathered in the city centre.
"The United States will monitor this situation, and we call on the government of Russia to immediately release all peaceful protesters," Mr Toner said.
"The Russian people, like people everywhere, deserve a government that supports an open marketplace of ideas, transparent and accountable governance, equal treatment under the law, and the ability to exercise their rights without fear of retribution."
US President Donald Trump is under intense pressure over his Russia ties, amid an FBI probe of Russian interference in last year's presidential election, including Moscow's possible collusion with Trump's campaign.