There has been widespread criticism of the conviction and jailing of Alexei Navalny, a Russian protest leader.
Navalny, 37, was sentenced in Kirov on Thursday to prison for five years for embezzlement from a timber company. He denied the charges, saying the trial was politically motivated.
The European Union said the verdict poses serious questions about Russian law and the United States says it is deeply disappointed.
White House spokesman Jay Carney said the sentence was the latest example of a disturbing trend of government actions aimed at suppressing dissent in Russia.
Amnesty International said the court case was a parody of a prosecution and a parody of a trial.
Navalny was a leading campaigner against United Russia party of President Vladimir Putin and regularly blogged about corruption.
Cormer cabinet minister Boris Nemtsov told reporters the trial was "completely fabricated from start to finish, and even the judge could not say what the reason for the crime was".
The BBC reports Navalny recently registered his candidacy for the next mayor of Moscow. After the verdict, his campaign team said he was withdrawing from the race and called on his supporters to boycott the vote.