Moscow (CNN) Russians were voting Sunday in a presidential election widely expected to cement President Vladimir Putin's rule for another six years.

Polls in the country's far east have already closed in an election involving 107.3 million voters eligible to cast ballots across the 11 time zones of the world's biggest country.

Putin cast his vote in Moscow on Sunday morning. "I am sure of the correctness of the course that I propose for the country," he said, according to state news agency RIA-Novosti.

Russian President Vladimir Putin exits a polling booth as he prepares to cast his ballot during Russia's presidential election.

Around 97,000 polling stations have been opened across this vast country, according to the Central Election Commission. Russians have a choice of eight candidates, including the communist Pavel Grudinin, a fruit-farm millionaire and Ksenia Sobchak, the daughter of Putin's political mentor.

Russian opposition leader Alexei Navalny has called for a boycott of the election since he was squeezed out of the race.

Opposition activists as well as the non-governmental election monitoring group Golos were reporting voting irregularities on Sunday afternoon.

By early evening, Golos had counted 2,000 incidents, including observers prevented from carrying out their work.

Navalny himself tweeted a link to a video that purported to show ballot stuffing, where people post multiple votes in one ballot box, in a polling station in Russia's far east.

Russia's Central Election Commission has pledged to investigate irregularities, and has suspended two officials amid allegations of voting fraud in the Moscow working-class district of Lyubertsy, according to the Russian news agency TASS.

It also claimed that its own website became the target of a hacking attack from 15 different countries before the polls opened, TASS reported.

Turnout a concern

The biggest threat to the current team at the Kremlin in this election is a low turnout. The concern is that bored voters, certain that Putin will easily be re-elected, may not bother to vote.

With just hours to go before polls closed, election officials said turnout was high, at almost 52%.

The big push to get the vote out has been aided by a social media campaign.

One video shows newlyweds arriving at a polling station in Tatarstan after tying the knot, the bride in a gorgeous white dress, accompanied by 40 wedding guests. Another tweet shows how to entice voters: put out a smorgasbord overflowing with food -- right in the middle of the polling station.

In Moscow, some people voting were offered free food to eat, while there was heavily discounted food available for sale elsewhere.

Presidential candidate Ksenia Sobchak smiles as she speaks to the media after voting during the Russian presidential election in Moscow.

Too many 'joke candidates'

A wave of anti-government protests in the past year suggests growing fatigue with corruption scandals seeping through the Kremlin and Putin's inner circle of oligarchs.

Nonetheless, Putin is genuinely a popular figure among many Russians, who see him as a strongman who lifted the country out of post-Soviet chaos to stability.

A woman exits a polling booth as she prepares to cast her ballot in the presidential election in Moscow.

Great-grandmother Valentina Ivanova, 76, explained to CNN in Moscow why she was voting.

"It's a holiday... one that's important for me and my family and my country."

"My country is getting stronger -- its always been strong -- and we approve of the direction it's going in. But the most important thing is peace. We're a peaceful people. We would like out grandchildren to have peace and an overall good quality of life. My family are internationalists."

Yugene Yarmakov, 23, who was voting for the first time, said there were too many "joke candidates."

"I don't believe I'm going to influence anything," he told CNN.

Russia-UK relations plunged into turmoil over the poisoning of a Russian ex-spy, his daughter and a police officer on British soil earlier this month. British Prime Minister Theresa May said it was "highly likely" the Kremlin was behind the attack, and both countries have expelled diplomats in an ongoing tit for tat.

Russia has also vowed to retaliate after the United States imposed new sanctions on the country this week over its reported cyberattacks and meddling in the 2016 presidential election. In both cases, Moscow has dismissed the accusations of involvement in the attacks.

Military sailors cast their ballots at a polling station in the Russian far eastern port city of Vladivostok.

But such conflict with international powers is unlikely to hurt Putin at home.

In fact, he may be banking on confrontation with international players this election. His United Russia party helped parliament move the date of the vote to the fourth anniversary of Russia's annexation of Crimea from the Ukraine. Annexing the Crimean Peninsula in 2014 redefined Russia's role on the world stage and marked the beginning of new, heightened tensions with Western powers.

Voters in Sevastopol, Crimea were given a medal engraved "With Russia forever," RIA-Novosti reported, to commemorate the 2014 independence referendum, considered illegitimate by Ukraine, the US and its European allies.

Only diplomats vote in Ukraine

In a sign of continued tension between Kiev and Moscow, Ukraine said Sunday it would not allow Russians in the country to vote at Russian consulates, according to a statement from the government information agency, Ukrinform.

The statement said only diplomats would have access to Russian diplomatic institutions on Ukrainian territory during the vote "in order to avoid provocations and possible grave consequences." Russian diplomatic buildings in Ukraine would be heavily guarded by Ukrainian police, it added.

Another Russian Presidential candidate is the ultra-nationalist Vladimir Zhirinovsky, leader of the Liberal Democratic Party of Russia.

"These are elections of the supreme ruler not only of Russia, but of the entire Planet Earth," he said after having cast his vote in Moscow.