Russia's state communications watchdog said on Wednesday (March 10) it was slowing down Twitter's speed to restrict its use, accusing it of failing to remove banned content from its site.
Twitter, like other U.S. social media, is used widely inside Russia by allies of Kremlin critic Alexei Navalny, whose jailing last month prompted vast nationwide protests.
The regulator, Roskomnadzor, threatened to block the social media service completely and said there were more than 3,000 posts containing illegal content on it as of Wednesday.
The service will be slowed on all mobile phones and half of non-mobile devices, it said.
And if Twitter carries on flouting the Kremlin's rules, it said enforcement will continue in line with the regulations - i.e., the site will be blocked.
Twitter did not immediately respond to requests for comment.