Moscow (dpa) - Russia has fined Twitter for refusing to delete tweets calling on young people to protest against the imprisonment of prominent Kremlin critic Alexei Navalny.

A court in Moscow ruled on Friday that the US social media company failed to delete public calls for minors to take part in demonstrations in mid-January, ordering it to pay a total of 8.9 million roubles (118,000 dollars).

According to the Interfax news agency, the court was also planned to later rule on similar accusations against Facebook made by Russia's media authority Roskomnadzor.

Roskomnadzor had already announced corresponding fines against social networks at the beginning of the year.

At the end of January, tens of thousands of people took to the streets in numerous Russian cities to demand the release of popular opposition politician Navalny, who has since been incarcerated in a prison camp.

The judiciary accuses Navalny's associates of deliberately calling on minors to take part in the unauthorized rallies via social media. The 44-year-old's supporters, however, say this is a pretext to halt protests and pursue organizers.

Because Twitter is also said to have failed to delete other banned posts - including child pornography - some Twitter content has been loading at lower speeds for many users in Russia in recent weeks.

Roskomnadzor has even threatened the social media platform with a blanket ban.

Critics see this as an attempt to restrict the right to freedom of expression on social networks. Hundreds of websites are already blocked in Russia, including those of government opponents.