Russian police on Saturday beat with batons and detained protesters who gathered outside Moscow's high-security prison holding top Kremlin critic Alexei Navalny, an AFP journalist reported.

Hundreds of demonstrators outside the Matrosskaya Tishina prison chanted "Freedom" and called on authorities to release President Vladimir Putin's most vocal critic, after an estimated 20,000 people gathered in the Russian capital for anti-government demonstrations.

The OVD-Info monitoring group said that law enforcement detained 2,131 demonstrators at protests in dozens of cities held across Russia Saturday calling for Navalny's release and denounce Putin's rule.

The group said that a majority of the detentions -- 795 -- were carried out in Moscow where protesters clashed violently with police.

The NGO said that more than 300 people were seized by police in Russia's second city Saint Petersburg, where an AFP journalist said more than 10,000 people rallied.

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