* Refugee influx fuels discontent with traditional parties
* Sweden Democrats thrive on fears over immigration, welfare
* Neither main political bloc secures a majority
* Opinion poll graphic https://tmsnrt.rs/2LmSZFD; Economic snapshot in charts http://tmsnrt.rs/2bylYpf
* Swedish election TAKE-A-LOOK: (Adds context, details, quotes)
By Daniel Dickson and Esha Vaish
STOCKHOLM, Sept 9 (Reuters) - Sweden's centre-left and centre-right blocs were neck-and-neck in an election on Sunday with the nationalist Sweden Democrats set to become the second biggest single party, exit polls indicated, as one of Europe's most liberal nations turns right amid fears over immigration.
Far-right parties have made spectacular gains throughout Europe in recent years amid growing anxiety over national identity and the effects of globalisation following conflict in the Middle East and Africa.
In Sweden, the influx of 163,000 asylum seekers in 2015 - the most in Europe in relation to the country's population of 10 million - has polarised voters and fractured the political consensus.
The ruling centre-left Social Democrats and Greens and their Left Party parliamentary allies were seen winning 39.4 percent of the vote, while the opposition centre-right Alliance were seen at 39.6 percent.
The Sweden Democrats, a party with white supremacist roots, rose to 19.2 percent from 12.9 percent in the previous election, the poll by public service broadcaster SVT suggested, leaving them holding the balance of power.
Another, smaller poll by TV4 had the Sweden Democrats taking 16.3 percent.
"I think we are going to top 20 percent and maybe a bit more than that, so I am still hopeful it can go up even more than we see now," Sweden Democrat party secretary Richard Jomshof said on the sidelines of an election rally in central Stockholm.
"We want to be a part of a government."
A partial tally of the vote by the Election Authority is due between 2000 and 2100 GMT, and in the past elections, exit polls have underestimated the final result for the nationalists.
With neither main political bloc able to command a majority, the Sweden Democrats, who want the country to leave the European Union and put a freeze on immigration, could play a decisive role in what looks set to be complex and drawn out negotiations over forming a government.
Sweden has flirted with populism before. New Democracy, founded by an aristocrat and a record producer, won nearly 7 percent of the vote in 1991, on the promise of strict immigration policies, cheaper alcohol and free parking, only to crash out of parliament three years later.
Nevertheless, should the Sweden Democrats get a fifth of the vote it would shake the country's image as a torchbearer for progressive values and trump the 12.6 percent for the far-right Alternative for Germany, which swept into the Bundestag last year.
With an eye on the European Parliament elections next year, Brussels policymakers are watching the Swedish vote closely, concerned that a nation with impeccable democratic credentials could add to the growing chorus of euroscepticism in the EU.
The record levels of asylum seeks in 2015 magnified worries about a welfare system that many voters already believe is in crisis, even though refugee numbers have fallen sharply since then.
Lengthening queues for critical operations, shortages of doctors and teachers and a police service that has failed to deal with inner-city gang violence have shaken faith in the "Swedish model", built on a promise of comprehensive welfare and social inclusion.
Sweden Democrats leader Jimmie Akesson has labelled the vote a choice between immigration and welfare in election campaign that has been unusually antagonistic.
"It has been really unpleasant," student Katze Collmar, 32, said while voting in central Stockholm.
"It feels like Sweden could take a step in this election that we won't be able to recover from very easily."
Mainstream politicians have so far refused to cooperate with the Sweden Democrats.
But with some kind of cooperation between parties in the centre-left and centre-right blocs an equally unlikely alternative to the current political deadlock, analysts believe that Akesson may yet end up with some influence on policy.
The Sweden Democrats have promised to sink any government that refuses to give the party a say in policy, particularly on immigration. With potential deadlock looming, it could take weeks to form a government.
(Additional reporting by Johan Sennero, Johan Ahlander, Helena Soderpalm, Johannes Hellstrom, and Reuters TV Writing by Justyna Pawlak and Niklas Pollard Editing by David Evans)
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