Russians started voting on Sunday in presidential polls likely to return strongman Vladimir Putin to the Kremlin for a record third term amid protests unseen since the Soviet era.

Voters in the far east of the world's largest country began casting their ballots at 2000 GMT in a marathon election straddling nine time zones which will close in the western exclave of Kaliningrad 21 hours later at 1700 GMT.

"The polling stations opened as scheduled. Everything is calm," Oksana Balynina, deputy head of the election commission in the resource-rich Chukotka region, said.

Live video images streamed by an official election website showed crowds of people queueing to vote at a polling station in the city of Anadyr just after its early morning opening.

The other regions to vote first were diamond-mining Yakutia, Sakhalin island, Kamchatka, and Magadan, the site of Soviet-era Gulag camps.

Victory for 59-year-old ex-KGB spy Putin appeared inevitable, with state pollsters forecasting a first-round win with 60 percent of the vote, leaving his Communist rival Gennady Zyuganov – a dour but seasoned lawmaker who is running for the fourth time -- trailing in second place with 15 percent.

The tycoon Mikhail Prokhorov and the flamboyant but ultimately pro-Kremlin populist Vladimir Zhirinovsky are expected to battle for third place while the former upper house speaker Sergei Mironov is tipped to finish last.

Putin's expected landslide victory may however be tainted by political uncertainty unknown during the current prime minister's first two terms as president between 2000 and 2008.

Street protests unprecedented in recent years that erupted in response to a fraud-tainted December parliamentary ballot have swelled into a broader opposition movement whose reliance on social media echoes the Arab Spring revolts.

Independent election monitors who are publicising alleged violations via the Internet during the polls have suggested that the authorities have been keen to minimise accusations of fraud during pre-election campaigning because of the protests sparked by the parliamentary polls.

The only difference during the presidential campaign was that "the methods of pressure on voters are more carefully organised, with a greater fear of publicity and public scandals", observer group Golos (Voice or Vote) said in a pre-poll statement.

The largest demonstrations have so far been confined to Russia's main cities and the authorities point to opinion polls showing the anti-Putin cause is only backed by a minority.

Yet Moscow has played a crucial role in recent Russian political events and police said they were drafting in an extra 6,300 police from the surrounding regions to make sure that Monday's planned post-election rallies do not spill over into Red Square.

"We are going to respond to provocations with the full force allowed by law," Moscow police chief Vladimir Kolokoltsev announced.

Putin ‘very happy’

Putin himself has put a brave face on the unexpected show of public displeasure by saying this week that he was ‘very happy about this situation’.

"I think this is a very good experience for Russia," he said.

His four challengers have all admitted to only having the ambition of finishing second and possibly joining a runoff should Putin fail to pick up 50 percent of the vote.

"I really want to make it into the second round," the metals magnate Prokhorov remarked before attending a Friday night campaign concert.

Meanwhile Putin in his last address to the nation on Friday appeared relaxed, advising that the country ‘must work smoothly and constructively, without shocks or revolutions’.