Russian Kremlin critic - Alexei Navalny - has been sent to a penal colony outside Moscow to serve his prison sentence.
Navalny was arrested last month on his return from Germany, where he had been recovering from a near-fatal poisoning in Siberia.
Several European authorities have said that Navalny was targeted with a novichok nerve agent developed in Russia.
He's now serving a two and a half year sentence for allegedly violating parole in a 2014 fraud case.
Navalny will be quarantined as a precaution, before he joins other prisoners in the colony.
The institution is located in the town of Pokrov and is known for its severe conditions.
Jailed Russia - a prisoners' rights group - says inmates are abused if they violate a strict daily schedule.
It adds that many prisoners cooperate with the colony administration and help them to control other inmates closely.
Navalny is one of Russian President Vladimir Putin's most prominent critics.
He accuses Putin of ordering his attempted murder and says the charges against him are jumped up.
Putin has dismissed that, alleging Navalny is part of a U.S.-backed dirty tricks campaign to discredit him.
The EU is preparing targeted sanctions against senior Russian officials over Navalny's jailing.