Russia's communications regulator on Saturday ordered media to remove reports describing Moscow's attack on Ukraine as an "assault, invasion, or declaration of war" or face being blocked and fined.
In a statement, Roskomnadzor accused a number of independent media outlets including television channel Dozhd and the country's top independent newspaper Novaya Gazeta of spreading "unreliable socially significant untrue information" about the shelling of Ukrainian cities by the Russian army and civilian deaths.
On Thursday, Russian leader Vladimir Putin unleashed a full-scale invasion of Ukraine that has killed dozens of people, forced more than 50,000 to flee Ukraine in just 48 hours and sparked fears of a greater conflict in Europe.
Citing a request from the General Prosecutor's Office, the communications regulator said the media outlets that also include Echo of Moscow radio will be blocked unless they remove the "unreliable information."
"Roskomnadzor also launched an administrative investigation into the dissemination of unreliable publicly significant information by the above-mentioned media," the watchdog said.
The offence is punishable by a fine of up to five million rubles ($60,000), it said.
Roskomnadzor also said that "reliable information" could be found in "official Russian information outlets."
Moscow has not so far provided any details of Russian losses in the fighting in the face of statements from Kyiv that they have inflicted heavy casualties on Moscow's forces.
The invasion of Ukraine is taking place during an unprecedented crackdown on the Russian opposition, with top protest leaders assassinated, jailed or forced out of the country.