Kremlin critic Alexei Navalny has revealed he has been taken to a Russian prison camp notorious for its strict control of inmates.

It comes about a month and a half after he was ordered to spend the next two years and eight months in jail, in a court ruling that was criticised internationally.

The 44-year-old is being held in the Vladimir region about 100 kilometres east of Moscow, a message posted on his Instagram account said on Tuesday morning (Australian time), along with a photo of himself with a very short haircut.

“I have to admit that the Russian prison system was able to surprise me,” Mr Navalny wrote.

“I had no idea that it was possible to arrange a real concentration camp 100km from Moscow.”

He is under constant surveillance, he said, adding that “video cameras are everywhere, everyone is watched and at the slightest violation they make a report”.

“But if you take it with humour, it is possible to live,” Mr Navalny wrote.

“I think someone upstairs read Orwell’s 1984 and said: ‘Yeah, cool. Let’s do this. Education through dehumanisation’,” he added.

Although he believes the numerous media reports about torture in the camp, he has not observed any violence so far, he wrote.

At the end of last week, it became known that Mr Navalny had been taken away from a pre-trial detention centre but there had been no sign of life from him for days after that.

On Tuesday, the opposition leader’s lawyers said they waited for hours outside the camp for information but received none.

Over the weekend, numerous users on social networks called for information about his whereabouts under the hashtag “Where is Navalny”.

At the beginning of February, Mr Navalny was sentenced to several years in prison for violating parole conditions in an earlier criminal case – he was at the time recovering from a poison attack in Germany.

-with AAP