Moscow - Russians voted on Sunday in an election set to hand President Vladimir Putin a fourth Kremlin term, as the country is embroiled in a crisis with Britain and its allies over a spy poisoning.With the vast country stretching across 11 time zones, polls opened in the Russian far east at 20:00 GMT on Saturday and will close in Kaliningrad, the country's exclave on the EU border, at 18:00 GMT on Sunday. With Putin's main challenger Alexei Navalny barred from taking part in the poll for legal reasons, the result of the election is hugely predictable, with overall turnout remaining the only likely element of surprise.Many analysts say that after 18 years of leadership - both as president and prime minister - Putin fatigue may be spreading across the country, and a lot of Russians are expected to skip the polls.The Kremlin needs a high turnout to add greater legitimacy for a new mandate for Putin, who is already Russia's longest-serving leader since Joseph Stalin.'A staged procedure' Casting his ballot in Moscow, Putin said he would be pleased with "any" result that gave him the right to continue serving as president. "I am sure the programme I am offering is the right one," Putin was quoted as saying by Russian news agencies.Navalny has denounced the election as a sham and urged Russians to boycott the vote. He has deployed more than 30 000 observers to monitor the polls and on Sunday, his team began publishing a rolling list of violations from polling stations around the country. Rather than call it a vote, Navalny's team is referring to Sunday's election as "a staged procedure to re-appoint Putin"."Those who said that 'there would be fewer falsifications during these elections because Putin has already won over everyone' have made a mistake," he said.In the run-up to the poll, a new crisis broke out with the West after Britain implicated Putin in the poisoning of former double agent Sergei Skripal with a Soviet-designed nerve agent.And Washington slapped sanctions on Moscow over alleged election meddling.Total control Since first being elected president in 2000, Putin has stamped his total authority on Russia, muzzling opposition and reasserting Moscow's posture abroad. He has sought to use the campaign to emphasise Russia's role as a major world power, boasting of its "invincible" new nuclear weapons in a major pre-election speech.His previous Kremlin term has been marked by a severe crackdown on the opposition, the annexation of Crimea, support for an insurgency in eastern Ukraine, an ongoing military intervention in Syria and the introduction of European and US sanctions -- all to the backdrop of a huge deterioration in ties with the West.But the 65-year-old former KGB officer is certain to extend his term to 2024 despite a litany of domestic problems like widespread poverty and poor healthcare following a lacklustre campaign.'Economy is terrible' Valentina Popova, a 77-year-old retiree, said she supported Putin's foreign policies and would vote for him."There's no alternative to him," she told AFP at a polling station in the south of Moscow. "I respect him for the foreign policy, otherwise Russia would perish."In Saint Petersburg, the former imperial capital, Antonina Kurchatova also said she voted for Putin but was just hoping things in Russia would not get worse."I very much like his foreign policy. He's doing everything right. But as far as the economy is concerned, everything is terrible," the 40-year-old told AFP.State-run pollsters predict Putin will take just under 70 percent of the vote, with the independent Levada Centre - branded a "foreign agent" - barred from releasing any research related to the election.Sunday marks exactly four years since Putin signed a treaty declaring Crimea to be a part of Russia after its annexation from Ukraine in a move that triggered the outbreak of a pro-Kremlin insurgency in the east of the ex-Soviet country. That conflict has since claimed more than 10 000 lives.Kiev has said Russians living in Ukraine would not be able to vote in Sunday's election as access to Moscow's diplomatic missions would be blocked.Push to boost turnout Putin is standing against a motley crew of seven challengers, including millionaire communist Pavel Grudinin and former reality TV host Ksenia Sobchak, but none are polling more than eight percent. Overall turnout is expected to be between 63 and 67 percent, according to official pollsters.Stepan Goncharov of the independent Levada Centre told AFP the pollster expected turnout to be between 57 and 68 percent.Authorities have pulled out all the stops to ensure a huge turnout, offering food discount vouchers and prizes for the best selfies taken at polling stations after running a sexually-charged online campaign.Students have been warned they may face problems or even expulsion if they do not turn out to vote, and heads of state enterprises have put pressure on their employees to go to polls.Putin first became president after Boris Yeltsin sensationally resigned on New Year's Eve 1999. At the end of his second term in 2008 he handed power to his protege Dmitry Medvedev.Putin then served a term as prime minister - although few doubted who was really in charge - and returned as president in 2012.The run-up to Russia's last presidential election in 2012 was marked by huge protests across the country against Putin's return as head of state.But those demonstrations were quashed, and once he was back in the Kremlin a crackdown ensued, with activists arrested, the Pussy Riot rock band jailed and draconian new laws passed which criminalised popular protest.