Hundreds of people, including a key opposition leader, were arrested in Russia on Sunday as thousands participated in unsanctioned protests against corruption and the anti-democratic tendencies of the ruling government.

A reported 500 people were detained in Moscow alone, where opposition leader Alexei Navalny, who has accused both President Vladimir Putin and Prime Minister Dmitry Medvedev of corruption, was also taken into custody.

Demonstrators in Moscow and other dozens of other cities, according to reports, we heard chanting, "Down with Putin!", "Russia without Putin!" and "Putin is a thief!".

The state-owned media outlet RT provided raw footage from the demonstrations:

According to Reuters:

The protests, reckoned to be the biggest since a wave of anti-Kremlin demonstrations in 2011/2012, come a year before a presidential election which Putin is expected to contest, running for what would be a fourth term.

Opinion polls suggest the liberal opposition, which Navalny represents, have little chance of fielding a candidate capable of unseating Putin, who enjoys high ratings. But Navalny and his supporters hope to channel public discontent over official corruption to attract more support.

A Reuters reporter saw police detain Navalny, who hopes to run against Putin, as he walked along central Moscow's Tverskaya Street with supporters, part of an unsanctioned rally as a police helicopter circled overhead.

Police put Navalny in a truck around which hundreds of protesters crowded, trying to open its doors.

Offering some of the backstory to Sunday's protests, the BBC explains:

Navalny called for the nationwide protests after he published reports claiming that Mr Medvedev controlled mansions, yachts and vineyards - a fortune that far outstripped his official salary.

Mr Medvedev's spokeswoman called the allegations "propagandistic attacks", but the prime minister himself has not commented on the claims.

The reports included the accusation that Mr Medvedev had a special house for a duck on one of his properties - and on Sunday, some demonstrators held up images of yellow rubber ducks.

Others showed up with their faces painted green, a reference to a recent attack in which Mr Navalny was hit with green liquid.

Though state media have typically ignored such protests in recent years, Vladimir Kuznetsov and Jake Rudnitsky, reporting for Bloomberg said its potentially significant that "sporadic coverage" of the demonstrations were provided.

They also report that at least one lawmaker,  Frants Klintsevich of the ruling United Russia party, "seemed sympathetic" to the protesters' concerns and demands.

"These demonstrations," Klintsevich said, "probably raise a lot of justified criticisms and concerns."