Thousands of demonstrators took to the streets in Moscow on Sunday to criticize Russian President Vladimir Putin in the face of a proposed increase in the retirement age.

Reuters reported that people at the rally chanted “Putin is a thief” and “Away with the tsar.”

More than 6,000 people are believed to have attended the protests, according to a nongovernmental organization that counts rally attendance, but Moscow police put the number close to 2,500.

Putin has been under fire over the retirement age proposal, which would raise the retirement age from 60 to 65 for men, and from 55 to 63 for women. The proposal is intended to improve government finances, Reuters reported.

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However, Putin’s approval ratings have dropped and he has faced protests since the idea was announced in mid-June. Putin once said he would not raise the retirement age, and has tried to distance himself from the proposal, Reuters reported.

While Putin faces criticism over his domestic policies, he received positive reviews in Russia for his performance at a meeting with President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE earlier this month.

Trump, meanwhile, has endured fierce bipartisan criticism over his handling of the meeting, where he seemingly sided with Putin and cast doubt on the U.S. intelligence community's assessment that Russia interfered in the 2016 presidential election.

The president has sought to clarify those remarks since, but has undercut his own efforts by declaring Russian interference to be a "big hoax."