MOSCOW, March 17 (Xinhua) -- Russians will cast their ballots on Sunday to choose a new head of state in the seventh presidential election since the establishment of the country's presidential system in 1991.

According to the Central Election Commission, about 110 million Russian citizens are eligible to vote, among which some 1.88 million who live overseas can vote in Russian embassies and consulates.

Polling stations will be open 12 hours from 8 a.m. to 8 p.m. local time across the country spanning nine time zones. The voting will start from the Kamchatka Peninsula in the Far East and end in Kaliningrad region in the Baltic.

Voters in Russia's remote areas, some foreign countries and on seagoing vessels have cast their ballots from Feb. 25 to March 17.

Web cameras have been installed at the polling stations, and Russia has invited more than 1,000 observers from 86 countries and 14 international organizations to monitor the election.

Under the Constitution, any Russian citizen aged 35 years or above, who has resided in Russia for no less than 10 years and does not hold citizenship or right of residence in any other countries, can be elected president.

To win an outright victory in the polls, a candidate must gain more than 50 percent of the ballots. If none of the candidates wins in the first round, the two front-runners will enter a run-off three weeks later, when he or she will defeat the other by getting more votes.

Eight candidates will compete in the seventh presidential election, including the incumbent President Vladimir Putin, Pavel Grudinin from the Communist Party and head of the Liberal Democratic Party Vladimir Zhirinovsky.

According to a poll conducted by Russia's Public Opinion Foundation on March 12, the last survey before Sunday's election, 64.9 percent of the respondents said they would vote for Putin.

Putin was followed by Grudinin, who was supported by 6.7 percent of the respondents, and Zhirinovsky with 6.2 percent. The other five rivals had much weaker public support.

Putin became Russian president for the first time in 2000, when Boris Yeltsin stepped down. He was re-elected in 2004 and became president for the third time in 2012 after serving as prime minister for four years.

Russia's Central Election Commission will confirm the election results by March 29.