800 Russians were arrested over protests against Putin raising the country's retirement age

Russian police on Sunday arrested hundreds of people from across the country protesting the country's plans to increase the retirement age.

Over 800 people were detained, according to rights group OVD-Info, and at least 15 people were beaten.

St. Petersburg had the most arrests in the country, with 354 protesters detained, according to OVD-Info.

The protests were spurred by a decision by President Vladimir Putin to raise the country retirement age, sparking rare outcry from across the political spectrum. Next year, the retirement age for men and women gradually increase, and by 2036 it will have risen from 60 to 65 for men and from 55 to 60 for women.

Putin has been under pressure to make the change because of Russia's aging population and economic deficit, but unions have warned that raising the retirement age would mean that many people in Russia will miss out on a pension altogether, as the country's life expectancy is lower than in the West.

Protests have sprung up across the country in recent weeks, drawing in crowds of tens of thousands of people. Sunday's rallies coincided with elections in 85 of Russia's regions, including capital Moscow.

In Moscow, at least 2,500 protesters gathered in the iconic Pushkin Square and chanted "Putin is a thief!" and "No increase in the pension age!" the Guardian reported. Protesters ignored calls to disperse by police, and some began to march towards the parliament building and were beaten by police with batons.

Calls for Sunday's protests were made by jailed opposition leader and vocal Putin critic Alexei Navalny, who was jailed last month for breaking protest laws.

Navalny had published ads on Youtube urging Russians to protest against the pension age hike, which Google confirmed to The Guardian had been taken down after pushback from Russian officials over laws which ban political campaigning 24 hours before an election.

Putin's approval rating has slumped to a four-year low to around 67% after announcing the increase. Putin pledged in 2005 never to raise the national retirement age while in office.

Alexandra Ma contributed to this report.