Austrians are voting in a general election in which the frontrunner, conservative People’s Party (ÖVP) leader Sebastian Kurz, is just 31.
The far-right Freedom Party (FPÖ) and Social Democrats are competing for second place, opinion polls suggest.
The Social Democrats led the outgoing coalition with the ÖVP.
Immigration has been a dominant issue in the campaign and the FPÖ is thought to have its best chance in years of returning to government.
The party narrowly missed out on the presidency in December when Norbert Hofer was defeated by Alexander Van der Bellen, head of the Greens, who won with about 53% of the votes.
The election comes amid anxiety in Europe over the huge influx of undocumented migrants and refugees in 2015, which fuelled an electoral breakthrough by the far right in neighbouring Germany last month.
If the polls are correct, a political shake-up could be on the cards in Austria, the BBC’s Bethany Bell reports from Vienna.
After more than a decade in which the Social Democrats have led a coalition with the conservatives, the mood in Austria seems to be moving to the right, our correspondent says.
Mr Kurz, the outgoing foreign minister, reinvented the ÖVP after becoming leader in May, moving it rightward with promises to:
Shut down migrant routes to Europe
The FPÖ accuse Mr Kurz of stealing their policies. Their candidate, Heinz-Christian Strache, has called him an “imposter”.
If his party wins, as polls suggest it will, Mr Kurz would become the youngest leader in Europe, and analysts say his party is likely to go form a coalition with the FPÖ.
Mr Kern warned on Saturday that the country “was at the most important crossroads in decades”.
His own party has been struggling after several scandals including an online smear campaign against Mr Kurz.
The party’s campaign focused on economic growth, jobs and social justice.
After a tumultuous year with internal rifts, the pro-refugee Greens are among several smaller parties uncertain of reaching the 4% vote threshold required to enter parliament.
Traditionally, the winning party is tasked with forming the next government which, since the 1980s, has been a coalition with one of the other parties.
Under the late Jörg Haider, the Freedom Party was the junior party in two coalitions with the ÖVP, between 2000 and 2007.