Russia said on Friday it was partially limiting access to Meta Platforms Inc's Facebook, accusing it of "censoring" Russian media, the latest in a series of steps against U.S. social media giants.

Moscow has been trying to exert tighter control over the internet and big tech for years, something critics say threatens individual and corporate freedom, and is part of a wider crackdown against outspoken opponents of the Kremlin.

The state communications regulator said that Facebook had ignored its demands to lift restricts on four Russian media outlets on its platform - RIA news agency, the defense ministry's Zvezda TV and websites gazeta.ru and lenta.ru.

It was not immediately clear what Russia's restrictions on Facebook would involve. Last year Moscow slowed down the speed of Twitter in a punitive move.

"In accordance with the decision of the General Prosecutor's Office, starting from Feb. 25, partial access restrictions are being imposed by Roskomnadzor on the Facebook social network," the regulator, Roskomnadzor, said in a statement.

Facebook, which had no immediate comment, has already irked Russia's authorities. Moscow routinely fines the company small sums for what it says is a failure to delete illegal content quickly enough.

In December, it issued a much bigger fine of 2 billion roubles ($24.27 million) for what it described as a repeated failure to delete content.

Moscow has also increased pressure on domestic media, threatening to block reports that contain what it describes as "false information" regarding its military operation in Ukraine, where Russian missiles were pounding Kyiv and families cowered in shelters.