Renowned Russian writer Boris Akunin, who was declared a "terrorist" by Moscow and became the target of a criminal inquiry this week, says he fears the moves signal a new milestone in the country's history under Vladimir Putin.

"Putin's regime has clearly decided to take a very important new step on its way from a police, autocratic state to a totalitarian state," Akunin, who lives in exile, told Agence France-Presse in a video interview.

"Extending repression to the sphere of literature in such a traditionally literature-centred country as Russia is a major step."

In the wake of Russia's invasion of Ukraine in 2022, authorities have taken their crackdown to a new level, introducing censorship and shutting down independent media.

This week authorities sent shock waves across Russia's literary circles by adding Akunin's name to Moscow's list of "terrorists and extremists" and opening a criminal probe against him over his criticism of Russia's invasion.

The measures were announced soon after Putin said he would seek a fifth term in office in 2024.

"This has not happened since the Stalin era and the time of the Great Terror," Akunin said, referring to his "terrorist" designation.

One lawmaker, Andrei Gurulev of the United Russia ruling party, called him an "enemy" and said Akunin should be "destroyed."

'Show us Navalny alive'

Akunin is the pen name of Grigory Chkhartishvili, one of Russia's most popular and commercially succesful writers, best known for his historical detective novels.

He has never shied away from criticising Putin and left Russia after the annexation of Crimea in 2014.

A top publishing house, AST, this month said it would no longer publish Akunin's books and those of another anti-Kremlin writer, Dmitry Bykov.

Another publisher, which refused to follow suit, was raided by investigators.

Akunin joked that members of law enforcement were creating extra work for themselves by confiscating his books.

"What's also funny is that prosecutors will now read all my books to look for extremism," the 67-year-old quipped.

"I am a very prolific writer, I have written 80 books."

Akunin said he was afraid authorities were using the smear campaign against him to distract public attention from jailed Kremlin critic Alexei Navalny, whose whearabouts have not been known for the past two weeks.

"I would really like world leaders to present Putin with an ultimatum — show us Navalny alive. This is very important," he said.

Akunin also said he expected the crackdown against him and Bykov to be just the beginning.

He recently warned Russians who had left the country after the war not to return, writing on social media that "the night will grow even darker."

He said that as in any authoritarian system, Putin's Russia would continue its downward spiral, adding that he feared the authorities would then achieve total control of the internet and introduce exit visas.

"Two more steps and Russia will become a completely totalitarian state," he said.

'About to get really scary'

Akunin said Western leaders made a "strategic mistake" by misunderstanding the historical logic of the development of the Russian imperial state, saying any other leader in Putin's place would have behaved "exactly the same way".

"I spent 10 years writing the history of the Russian state in 10 tomes. I understand the architecture of the Russian state much better now."

He said Western nations were also making a mistake by alienating anti-Kremlin Russians who fled Russia.

"The tragedy is that the world where they rushed to find haven has not been friendly. And lots of people abroad found themselves in a very difficult situation," he said.

"Now some of them are returning back simply because no one needs them anywhere. This absolutely horrifies me, because they are returning to a place where things are about to get really scary."

Anti-Kremlin Russians are the best hope to unseat Putin and change Russia, which could soon become either "northern Iran" or "western China", Akunin said.

"I think it's already clear that it won't be possible to defeat Putinism militarily," he said, adding that change would come from within.

"This regime is more fragile than it seems."

Akunin, a UK citizen, said he now called three countries — Britain, France and Spain — home and used each one for inspiration.

"I very much depend on my surroundings, on the genius of the place," he said. "I write non-fiction in London. I write serious literature in the land of Chateaubriand, and I work on entertaining literature in sunny Spain."

It is not easy to be a Russian writer these days, but he would not renounce his roots.

"I have nothing else in my life except Russian culture."