LONDON (Reuters) - A Russian court is considering a prosecutor's request to designate a journalist who frequently criticises the war in Ukraine and his wife as an extremist grouping.

A spokeswoman for St Petersburg's court system said on Telegram that a claim against former Russian TV news anchor Alexander Nevzorov and Lidia Nevzorova had been filed by the city "in defence of the interests of the Russian Federation".

Nevzorov, 65, runs a YouTube channel with nearly 2 million subscribers where he often criticises the war in Ukraine. He and his wife fled Russia in March 2022 and now live in Europe.

The lawsuit seeks to ban the "extremist activities" of the "association" - meaning the couple - and to turn over the association's property to the Russian state, the court spokeswoman said.

Nevzorov was sentenced in absentia last year to eight years by a Russian court for spreading "fake news" about Moscow's army. He said he considered the lawsuit an escalation of authorities' attempts to silence him.

"I am now being tested by a method that will be applied to all fully-dissenting free-thinkers, foreign agents, and other enemies of Putin's regime," he told Reuters in a voice message.

"They tried to negotiate with me for a long time to stop telling the truth about the war and the degradation of the country. I didn't agree."

Russia's list of "extremist" groups include the Taliban, U.S. tech giant Meta, and what it calls the "LGBT movement". The designation effectively outlaws those entities' activities inside Russia and opens up avenues to pursue criminal cases against those perceived as associated with them.

The agency in charge of maintaining the list, Rosfinmonitoring, has the power to freeze the bank accounts of the more than 15,000 people and entities who carry the label.

The couple's lawyer, Alexei Pryanishnikov, said that Russia has never labelled a married couple as "extremist" before.

Nevzorov, who made his name hosting the pioneering news programme "600 Seconds" as Soviet society opened up under Mikhail Gorbachev and also served in Russia's parliament, was granted Ukrainian citizenship after publicly denouncing Russia's invasion, calling the war a "crime" and Ukraine its victim.

His wife, Nevzorova, a publisher, said the couple has no assets left in Russia, but she feared the lawsuit could target her mother, who still lives in the country.

"They want to deprive us of our livelihood and punish us in a showy manner," she told Reuters in a Telegram message. "And they want to take everything away from mum."

(Reporting and writing by Lucy Papachristou; Editing by Alison Williams)

By Lucy Papachristou