THE far-right Sweden Democrats party have made huge gains as mass immigration left the traditionally liberal country bitterly divided.
The party are poised to become "king-makers" as, with almost all the votes counted, neither of the leading alliances have reached the threshold to govern alone.
It is the most recent signal that isolationism and nationalism is gaining momentum in Europe.
More than seven million Swedes voted in the first election since the country allowed 163,000 migrants into the country in 2015.
With most of the ballots counted, the governing center-left bloc has a razor-thin edge over the center-right opposition Alliance, with roughly 40 percent each.
Current Prime Minister Stefan Lofven has already ruled ruled out cooperating with the Sweden Democrats (SD), who won 18 per cent of the vote.
The SD have been linked for years to Neo-Nazi and other far-right groups, but have made a number of attempts to rebrand itself since it entered Parliament in 2010.
The party, with white supremacist roots, rose from roughly 13 percent in the previous election, the poll by public service broadcaster SVT suggested, depriving either of the mainstream blocs of a parliamentary majority.
SD chairman Ulf Richard Jomshof said: "We want to be a part of a government."
A protracted battle to form a working coalition now looks certain.
A senior German official described Sweden's election as a "turning point" for Europe.
Michael Roth, a deputy foreign minister, was quoted as telling Monday's edition of German daily Die Welt saying Sweden had seen an emotional discussion about migration and said: "the gap between facts and perceived reality is getting ever bigger."
"Nationalist populism is still advancing, and it will complicate forming a government."
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.
Other European countries have seen support rise for anti-immigration parties amid growing anxiety over national identity and the effects of globalisation and fears over immigration following armed conflict in the Middle East and North Africa.
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Italy this year installed a new coalition government run by the anti-establishment Five Star and the right-wing League.
Meanwhile last year the far-right Alternative for Germany won 12.6 per cent of the vote, and The Danish People's Party won 21 per cent in 2015.
Acrimony between the two main political blocs has defined Swedish politics for decades, and the rise of the Sweden Democrats - long a pariah grouping in parliament - has hugely complicated the political landscape.
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