Voters across Russia are heading to the polls for three days from Friday to choose their next president. Incumbent President Vladimir Putin appears certain to win his fifth term.

What Russia calls voting in the election is also expected to take place in the Ukrainian regions of Crimea, Donetsk, Luhansk, Zaporizhzhia and Kherson.

Moscow unilaterally declared its annexation of Crimea in 2014 and the other four regions in September 2022, seven months after it began invading Ukraine.

Putin is up against three other candidates -- Nikolay Kharitonov of the Communist Party of the Russian Federation, Leonid Slutsky of the far-right Liberal Democratic Party of Russia and Vladislav Davankov of the New People party.

But a recent poll by the government-affiliated Russian Public Opinion Research Center, or VCIOM, indicates that Putin may get 82 percent of the vote.

Russian authorities have been rigorously tightening restrictions and monitoring of individuals and groups that carry out activities deemed to be out of line with the policies of the Putin administration.

The widow of the late Russian opposition leader Alexei Navalny urged people to protest against Putin by converging en masse at polling stations at noon on Sunday, the final day of voting.

Yulia Navalnaya called on them to deface their ballots, vote for any candidates except Putin, or simply stand at polling places and leave.

Russian authorities say Navalny died at an Arctic penal colony last month.

Analysts say Putin is aiming to win the election with at least 80 percent of the vote on voter turnout of 70 percent.

They say he will trumpet the overwhelming victory to claim people's approval of his policy agenda during the current term, including what Moscow calls its special military operation in Ukraine.

Vote counting is expected to begin soon after polling stations close on Sunday.