Russian Foreign Minister Sergei Lavrov said Thursday that Moscow's large-scale military intervention against Ukraine had "cleansed" Russian society, after thousands fled the country or were detained since fighting broke out.

Since the Kremlin ordered troops into Ukraine in February 2022, officials in Moscow have repeatedly branded as "traitors" Russians who fled the country to escape a sweeping mobilisation drive or for political reasons.

"The special military operation has united our society like never before and contributed to the cleansing of people who do not feel they belong to Russian history and culture," Lavrov said during a press conference.

"Some of those have left, some have stayed but have started to think", he added.

Tens of thousands of Russians left the country in protest at the start of the conflict, with thousands more leaving after the Kremlin announced a military mobilisation drive.

Moscow has also orchestrated a far-reaching crackdown on dissent, banning criticism of the military campaign and punishing thousands for publicly denouncing it.

It is not the first time Russia's leadership has referenced cleansing or purging society, while also vowing to "de-Nazify" Ukraine.

In May last year, President Vladimir Putin said: "I am certain that such a pure and necessary self-cleaning of society will only strengthen our country."

"Russian people can always distinguish real patriots from traitors and scum and just spit them out like a fly that accidentally flew into their mouth," the longtime Russian leader added.