Russian President Vladimir Putin's former adviser Gleb Pavlovsky died in Moscow on Monday after a serious illness at the age of 71, local media reported.

Once an influential figure in Russian politics, Pavlovsky served as a political adviser to President Vladimir Putin but later became a critic of the Kremlin.

Who was Gleb Pavlovsky?

Pavlovsky was born in the Ukrainian city of Odesa and was a dissident during the Soviet era. He served a sentence of internal exile in the northern republic of Komi in the 1980s.

In 1995, Pavlovsky co-founded the Effective Policy Fund, a political strategy firm that worked on the presidential campaigns of Boris Yeltsin and his successor, Vladimir Putin.

Pavlovsky worked as a Kremlin advisor and was a guiding figure during Putin's first two terms as president, from 2000 to 2008, and was primarily known for his role as a spin doctor and "political technologist."

He was instrumental in the development of Russia's "managed democracy" that marginalized, exiled, or jailed Putin's rivals.

However, he was dismissed after criticizing Putin and then-President Dmitry Medvedev's "castling" political maneuver, which allowed Putin — who had served for a term as prime minister — to run for a third term as president.

Pavlovsky then became a critic of the Kremlin, and became known as one of the most insightful opponents of the administration.

Reporting his death, the English-language Moscow Times newspaper described Pavlovsky as "one of the most eloquent voices on the machinations and intrigue taking place in the halls of power."

On Russia's invasion of Ukraine, Pavlovsky said it was a war that Moscow couldn't win. 

"The previous Putin would not have done this," he said soon after the invasion. "He was a very sane-thinking person. But this has all vanished now. He has an obsession about Ukraine that he didn't previously have. He is reacting now to the pictures in his own head."

Pavlovsky also took part in the unsuccessful 2004 presidential campaign of pro-Russian politician Viktor Yanukovych in Ukraine. Yanukovych was eventually elected to power but was removed from office and sent into exile in 2014. 

Following Yanukovych's departure from Ukraine, Russia annexed Crimea and began to back separatist proxy fighters in Ukraine's eastern Donbas region.

Edited by: Amanda Rivkin