Austria's presidential election remains on a knife-edge with all votes from polling stations now counted.
The interior ministry says that Norbert Hofer of the far-right Freedom Party is currently slightly ahead of his rival, Alexander Van der Bellen.
The result will only be decided when hundred of thousands of postal ballots are counted on Monday.
A key campaign issue was Europe's migrant crisis, which has seen asylum-seeker numbers soar.
About 90,000 people claimed asylum in Austria last year, equivalent to about 1% of the Austrian population, and the Freedom Party ran an anti-immigration campaign.
For the first time since World War Two, both the main centrist parties were knocked out in the first round.
The presidency is a largely ceremonial post, but a victory for Mr Hofer could be the springboard for Freedom Party success in the next parliamentary elections, scheduled for 2018.
The presidents of the European Commission and the European Parliament, Jean-Claude Juncker and Martin Schulz, have both expressed concern over a Hofer victory.
Analysis: Bethany Bell, BBC News, Vienna
Austria is split. The soft-spoken, charismatic Mr Hofer, sometimes described as a wolf in sheep's clothing, caused turmoil in Austrian politics when he won a clear victory in the first round of voting in April.
But now his rival, Mr Van der Bellen from the Greens, has caught up. The far right has profited from deep frustration with the established parties of the centre left and the centre right in Austria. And in recent months, it has been boosted further by fears about the migrant crisis.
If Mr Hofer wins, it could have an impact far beyond Austria's borders - possibly giving momentum to far-right and Eurosceptic parties in other EU countries.