Russian police on Wednesday detained one of the last opposition figures still in the country and not behind bars after he reportedly criticized Moscow's military campaign in Ukraine.

Politician Yevgeny Roizman, former mayor of the Urals city of Yekaterinburg, was detained for "discrediting" the Russian army in comments about Moscow's military intervention in Ukraine.

"The suspect was detained in Yekaterinburg and will be taken to Moscow for investigation," the Moscow branch of Russia's interior ministry said in a statement.

It said he faces criminal charges of "discrediting" the Russian army and will be brought to Moscow as part of the investigation.

The charges are punishable by up to 10 years in jail.

A dozen armed police in camouflage on Wednesday burst into the 59-year-old's home, according to a video posted on the Mash Telegram channel, reputed to be close to the Russian security services.

His lawyer Vladislav Idamzhapov later told state news agency TASS that Roizman had been placed in custody for 48 hours.

The Moscow police said Roizman posted a video online, "the contents of which discredited the use of" the Russian armed forces.

A police source quoted earlier by TASS said the video was published on the politician's YouTube channel.

In a video filmed outside his apartment on Wednesday, Roizman told reporters he was being charged for using the word "invasion" to describe what Russia calls its military operation in Ukraine.

Roizman has already been fined three times for criticizing Russia's offensive in Ukraine.

In a recent interview with AFP, Roizman said he has "no illusions" and understood that he could face arrest for his views.

"But I also have no fear," he said.

Roizman was a lawmaker between 2003 and 2007. In 2013, he became Russia's highest-profile opposition mayor and held the position for five years.

Last year he was sentenced to nine days in jail for urging people to join demonstrations in support of jailed Kremlin critic Alexei Navalny.

Almost all of President Vladimir Putin's prominent political opponents have either fled the country or are in jail.

Recently two opponents remaining in Russia, councilor Ilya Yashin and activist Vladimir Kara-Murza, were placed in detention for denouncing the Ukraine conflict, facing up to 10 years in prison.