Russian environmentalist Yevgeny Vitishko, who was sentenced to three years in prison during the Sochi Olympic Games, has been transferred to a penal colony almost 1,000 kilometres away, his organisation said Thursday.

After disappearing from a prison in Krasnodar earlier this week, Vitishko was sent to Tambov region which lies about 1,000 kilometres (620 miles) north of Sochi in central Russia, the Environmental Watch on North Caucasus (EWNC) said on its website, citing a letter from the penal service.

The letter, which was also posted by EWNC, states that Vitishko "has been sent to the penal service of the Tambov region for the rest of his punishment".

Vitishko lost his appeal on February 12 against a court decision to convert his suspended term to a real one, in the case of damaging a forest fence that dates back to 2012.

The International Olympic Committee had said that they have been "assured" by the Russian authorities that Vitishko's case is not related to the Olympic Games.

However Vitishko and the EWNC said the organisation is victim of a crackdown on critics of the Games, which ended Sunday, and is being punished for speaking out about environmental destruction in the sensitive Black Sea region.