MOSCOW, Feb. 16 -- The Kremlin's most prominent critic Alexei Navalny died Friday in an Arctic prison, said Russian authorities, announcing his death a month before an election poised to extend Vladimir Putin's hold on power.

Navalny's death after three years in detention and a poisoning which he blamed on the Kremlin deprives Russia's opposition of its figurehead at a time of intense repression and Moscow's campaign in Ukraine.

Dissidents and Western officials blamed Putin and his government for the 47-year-old's death, which followed months of deteriorating health in harsh detention conditions.

"Alexei Navalny was tortured and tormented for three years... Murder was added to Alexei Navalny's sentence," Russian Nobel Peace Prize winne...