Washington/Moscow, Mar 27 (IANS): The US State Department has "strongly condemned" the detention of hundreds of protesters throughout Russia including the country's opposition leader, the media reported.

Thousands took part to anti-corruption protests cross 80 Russian towns and cities on Sunday, with the largest held in Moscow and St. Petersburg, The Telegraph reported.

Moscow police told the TASS news agency that the number of people detained was "more than 500".

Police said those detained will face "administrative prosecution", or fines and arrests.

But the final tally of those detained in Moscow was 700, according to the human rights monitoring group OVD-Info.

Alexei Navalny, a campaigner who hopes to stand against President Vladimir Putin in next year's elections, was bundled into a police van on Sunday morning as he approached a group of protesters in Moscow's Pushkin Square.

In response, the State Department said it was "troubled" to learn of his arrest and called the detention of peaceful protesters "an affront to democratic values", spokesman Mark Toner said in a statement on Sunday evening.

"Detaining peaceful protesters, human rights observers, and journalists is an affront to core democratic values," Toner said.

"The US will monitor this situation, and we call on the government of Russia to immediately release all peaceful protesters."

"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," The Telegraph quoted Toner as saying.

The protests were triggered by a film produced by Navalny which claims that Prime Minister Dmitry Medvedev has seized a collection of yachts, several mansions and a vineyard through questionable means.

Medvedev is also alleged to have used a network of charity websites run by business associates to conceal his links to the deals.

It came after hundreds of demonstrators were also arrested in Belarus over the weekend during a protest in Minsk against a tax on the unemployed.