Russian opposition leader Alexey Navalny has been jailed for 15 days for his role in mass anti-corruption protests in Moscow.

Navalny, who was arrested at a Sunday's demonstration, was sentenced by a court in Moscow on Monday afternoon for resisting police orders, the BBC reported.

The verdict was tweeted by his press secretary.

Navalny was one of hundreds of people who were detained across the country in connection with the rallies, calling for the resignation of Prime Minister Dmitry Medvedev over corruption allegations.

Responding to the protests, the Kremlin accused the opposition of encouraging lawbreaking and provoking violence. Some young people were paid to attend, a presidential spokesman said.

In a tweet after his detention, Navalny had urged fellow protesters to continue with the demonstration.

"Guys, I'm fine. No need to fight to get me out. Walk along Tverskaya (Moscow main street). Our topic of the day is the fight against corruption," he wroye (in Russian).

Navalny, a lawyer and anti-corruption blogger who heads Russia's Progress Party, called for the nationwide protests after he published reports claiming that Medvedev controlled mansions, yachts and vineyards -- a fortune that far outstripped his official salary.

Medvedev's spokeswoman called the allegations "propagandistic attacks", but the Prime Minister himself has not commented on the claims.

Thousands of demonstrators attended rallies in St. Petersburg, Vladivostok, Novosibirsk, Tomsk and several other cities, as well as in Moscow, said the report.

In Moscow, protesters filled Pushkin Square and some climbed the monument to poet Alexander Pushkin shouting "Impeachment". Turnout was estimated to be between 7,000 and 8,000, according to the police.

The police said 500 protesters were arrested in the capital alone, but a rights group, OVD Info, put that number at 700, at least.

The marches appeared to be the biggest since anti-government demonstrations in 2011/2012, the BBC reported.

Meanwhile, the US State Department "strongly condemned" the detention of hundreds of protesters throughout Russia, including of Navalny.

The European Union's diplomatic service demanded the release of demonstrators who were arrested during anti-corruption protests.

In a statement, the European External Action Service (EEAS) said the detained citizens, including opposition leader Alexei Navalny should be released as they had the right to gather peacefully and to free speech.

The head of the Council of Europe on Monday also urged Russian authorities to release the opposition protesters.

The arrests "raise issues under the European Convention on Human Rights," Secretary-General Thorbjorn Jagland said.