An exit poll is projecting that nearly one in five Swedish voters backed an anti-immigrant party with white supremacist roots in the Scandinavian country's election.

However, Swedish broadcaster SVT said its poll from Sunday's election indicates that the centre-left Social Democrats governing Sweden now would remain the largest party in parliament.

The poll projects that the ruling party received 26.2% of the vote.

If the exit poll results carry over to the official count, the far-right Sweden Democrats would be the second-largest party in parliament.

The poll gave the party 19.2% of the vote.