(Reuters) — Russia opened a criminal case against Facebook's parent, Meta Platforms, on Friday after the social network changed its hate speech rules to allow users to call for “death to the Russian invaders’ in the context of the war with Ukraine.

Russian prosecutors asked a court to designate the U.S. tech giant as an "extremist organization," and the communications regulator said it was restricting access to Meta's Instagram.

“A criminal case has been initiated ... in connection with illegal calls for murder and violence against citizens of the Russian Federation by employees of the American company Meta, which owns the social networks Facebook and Instagram,” Russia's Investigative Committee said.

The committee reports directly to President Vladimir Putin. It was not immediately clear what the consequences of the criminal case might be.

No comment was immediately available from Meta in response to a Reuters request.

Two weeks into Russia's war in Ukraine, a Meta spokesperson said Thursday the company had temporarily eased its rules for political speech, allowing posts such as “death to the Russian invaders,” although it would not allow calls for violence against Russian civilians.

Meta said the temporary change aimed to allow for forms of political expression that would normally violate its rules. Its oversight board said Friday that it was closely following the war in Ukraine, and how Meta is responding.

Russia has for more than a year been striving to curb the influence of U.S. tech giants including Alphabet Inc.'s Google and Twitter, repeatedly fining them for allowing what it deems to be illegal content.

But the invasion of Ukraine — met by a storm of international condemnation and unprecedented sanctions — has sharply raised the stakes in the information war.

Social media provide an opportunity for dissent against Mr. Putin's line — loyally followed by the tightly controlled state media — that Moscow was forced to launch its "special military operation" to defend Russian-speakers in Ukraine against genocide and to demilitarize and “denazify” the country.

The Investigative Committee said the Facebook move could violate articles of the Russian criminal law against public calls for extremist activities.

“Such actions of the (Meta) company's management not only form an idea that terrorist activity is permissible but are aimed at inciting hatred and enmity towards the citizens of the Russian Federation,” the state prosecutor's office said.

It said it had applied to a court to recognize Meta as an extremist organization and prohibit its activities in Russia.

The United Nations human rights office said the potential change in Facebook policy was worrying.

“It is a very concerning issue because it does have a certain risk to generate and encourage and allow hate speech that is directed at Russians in general,” a spokeswoman said.

Meta's Facebook, Instagram and WhatsApp services are all popular in Russia, with 7.5 million, 50.8 million and 67 million users last year respectively, according to researcher Insider Intelligence.

Last week, Russia said it was banning Facebook in the country in response to what it said were restrictions of access to Russian media on the platform.