OVD-Info, a Russian human rights organisation, said other examples of people denounced by informers included a woman in Siberia who tied yellow and blue ribbons to a tree in the garden of her house, a Moscovite who hung a Ukrainian flag in the window of his flat and a regional police officer overheard complaining about the war.

Pupils at a school in Penza, central Russia, secretly taped their teacher making anti-war comments and denounced her to the police.

In the recording, published online by the exiled Baza news service, a 15-year-girl complained that she has been banned from travelling to Europe for a competition. Her teacher interrupted her and said that this could only be expected when Russia was bombing western Ukraine.

“We don’t know all the details,” the girl is heard protesting. The teacher replied: “I’ve read 100, 200 different independent sources and you haven’t read one. We live in a totalitarian regime… We are North Korea. We are an outcast country.”

“Denunciations are happening today, once again, in Russia,” said Alexandra Baeva, the head of the legal department at OVD-Info.

“In Russia now, it is like 1937. People are scared and informing on each other,” Ms Baeva said in a telephone interview from Moscow. Many of her liberal-minded friends have fled Russia since the start of the war, she said, but she chose to stay because “we have a human rights crisis”.