Chancellor Angela Merkel's spokeswoman Ulrike Demmer also called on Moscow to respect the freedoms of speech and assembly and to ensure international standards are met in September's municipal election.

Russian police arrested nearly 1,400 people as they gathered in Moscow at the weekend to demand free and fair elections, a monitor said Sunday, making it the biggest such crackdown in years.

Police used batons on protesters as they tried to gather outside city hall, and AFP reporters at the scene saw demonstrators with injuries.

Demmer said at a press conference that Germany had taken note of the "disproportionately tough police action with great concern" and now "expects the speedy release of those detained".

She did not make special mention of top Kremlin critic Alexei Navalny, who was jailed for 30 days for calling the fresh protest.

On Sunday, Navalny was rushed from jail to hospital suffering an acute allergic reaction, which his physician Anastasia Vasilyeva said may have been caused by a "toxic agent".