Russia's top independent newspaper Novaya Gazeta, whose chief editor last year won the Nobel Peace Prize, on Monday suspended publication until the end of Moscow's military action in Ukraine.

"For us and, I know, for you, this is a terrible and difficult decision," said chief editor Dmitry Muratov.

"But we need to save us for each other," he said in a statement, indicating that it was necessary to avoid a complete shutdown of the newspaper.

Co-founded by former Soviet leader Mikhail Gorbachev in 1993, Novaya Gazeta was the only main newspaper left voicing criticism of President Vladimir Putin and his tactics in and outside the country.

The announcement came more than a month into the Kremlin's military campaign in pro-Western Ukraine, with thousands of people killed and more than 10 million displaced in the worst refugee crisis in Europe since World War II.

"We have received another warning from Roskomnadzor," the newspaper said, referring to Russia's media regulator.

"We are suspending publication of the newspaper on our website, on social media and in print -- until the end of the 'special operation in Ukraine'," it added.

Earlier Monday, Novaya Gazeta staff learned of a formal warning from Roskomnadzor state communications watchdog, its second since last week.

Nadezhda Prusenkova, a Novaya Gazeta spokeswoman, told AFP that the newspaper still did not have a copy of the warning, adding that they had learnt about the development "from the news".

If a media outlet receives two warnings from the communications regulator in the space of a year, a court can shut it down.

"If we don't stop, we will be stripped of our licence through court," Prusenkova said.

Muratov said the formal warnings were payback for Novaya Gazeta's coverage of the conflict and its efforts to estimate "losses and destruction", both in Russia and Ukraine.

Josep Borrell, the European Union's top diplomat, decried the move, saying Novaya Gazeta had had to suspend its operations as a "result of censorship and following years of systematic intimidation by Russian authorities.

Chief editor Dmitry Muratov said it was a 'terrible and difficult decision'
Chief editor Dmitry Muratov said it was a 'terrible and difficult decision' AFP / Dimitar DILKOFF

"The EU will continue to counter the Kremlin's disinformation campaigns and support Russian independent media and journalists in their important work," he said in a statement.

The newspaper got into hot water with Russian authorities even after it said it would have to work "under conditions of military censorship".

In early March, the media outlet said it would have to comply with newly adopted legislation after lawmakers introduced jail terms of up to 15 years for publishing "fake news" about Russia's army.

But it still published stories from Ukrainian cities including Kyiv, Mykolaiv and Odessa.

Last week, Roskomnadzor said Novaya Gazeta had failed to mark a non-governmental organisation mentioned in one of its stories as a "foreign agent" in accordance with Russian legislation.

Russia is seeing an unprecedented crackdown on dissenting voices and independent journalism, which has included dubbing NGOs and media outlets "foreign agents" -- a label that carries strong pejorative connotations and implies increased government scrutiny.

Novaya Gazeta itself has not been declared a "foreign agent".

Even in the current conditions the newspaper's announcement came as a jolt.

"That's it, there is no more independent media in the country," wrote StalinGulag, a prominent opposition blogger. "Complete censorship."

Media watchdog Reporters Without Borders urged the Russian authorities "to stop these policies of censorship".

In early March, Echo of Moscow radio was disbanded while independent TV channel Dozhd TV decided to suspend operations.

Last year, Muratov was awarded the Nobel Peace Prize jointly with Maria Ressa of the Philippines for their efforts "to safeguard freedom of expression".

Muratov said last week the newspaper had decided to donate the gold medal to a fund to help Ukrainian refugees.

Since 2000, six of Novaya Gazeta's journalists and collaborators have been killed in connection with their work, including investigative reporter Anna Politkovskaya.