Former National Security Agency contractor Edward Snowden Sunday criticized the integrity of Russia’s presidential election just before exit polls showed President Vladimir Putin had easily won a fourth term in office.

“The ballot stuffing seen today in Moscow and elsewhere in the Russian election is an effort to steal the influence of 140+ million people,” Snowden said in a tweet. “Demand justice; demand laws and courts that matter. Take your future back."

The ballot stuffing seen today in Moscow and elsewhere in the Russian election is an effort to steal the influence of 140+ million people. Demand justice; demand laws and courts that matter. Take your future back. https://t.co/Jh6W8gq7Zx — Edward Snowden (@Snowden) March 18, 2018

Snowden was granted asylum in Russia in 2013 after he leaked secret information from the National Security Agency's surveillance programs, and has been there ever since.

Critics have slammed the election as a sham, noting the Kremlin had banned opposition activist and leading Putin opponent Alexei Navalny from the ballot, and imposed restrictions on some election monitors.

Independent election observers and activists have alleged numerous incidents of ballot stuffing and other irregularities in Sunday's vote.

The non-governmental election monitoring group Golo has flagged at least 2,000 incidents, including observers being prevented from monitoring voting locations.

Putin is already Russia's longest-serving leader since Soviet dictator Joseph Stalin.