Russian prosecutors on Thursday banned Meduza, a popular and independent Russian-language news website, saying it posed a security "threat" to the country.
Russian authorities have been presiding over an unprecedented media and opposition crackdown since President Vladimir Putin sent troops to Ukraine in February.
Meduza was established in 2014 and is based in Latvia to circumvent Moscow's censorship.
On Thursday, the general prosecutor's office said that it was designating Meduza an "undesirable" entity, upping pressure on the media outlet.
"It has been established that its activities pose a threat to the foundations of the constitutional order and the security of the Russian Federation," prosecutors said in a statement.
Meduza had already been branded a "foreign agent" in Russia in 2021.
Under the "undesirables" law, Russians who maintain ties with such organisations -- from reporters to readers -- could face heavy fines or even prison terms of up to six years.
Since Putin sent troops to Ukraine, all independent media in Russia have been shut down or have suspended activities.
Access to the websites of foreign-based media, such as Meduza, has been restricted.
The "foreign agent" label -- reminiscent of the "enemy of the people" of the Soviet era -- has in recent years been used extensively against opponents, journalists and rights activists in Russia.
On Wednesday, a Moscow court ordered the closure of Russia's oldest human rights organisation, the Moscow Helsinki Group.
