Russian President Vladimir Putin has overseen a ruthless crackdown on dissidents and critics during his 24 years in power, and all his major domestic opponents are now dead, exiled or in prison.
His staunchest critic of the last decade, Alexei Navalny, died last month in an Arctic prison colony.
Thousands turned out to mourn him at his funeral in Moscow, some voicing rare dissent in the streets of the capital.