Voting is under way in Slovenia's presidential run-off amid growing discontent with cost-cutting measures designed to avoid an international bailout.

Sunday's runoff pits anti-austerity incumbent Danilo Turk against former Prime Minister Borut Pahor, who has supported some of the government's budget measures during his campaign.

Voting began at an even slower pace than in the first round, when the final turnout dropped to a record low.

By 11 am, four hours into the vote and with eight remaining, just 12.4 per cent of the electorate had cast their ballots, the state election commission said.

In the November 11 first round, the turnout at the corresponding time was 14.4 per cent, reaching just over 48 per cent for the entire day.

The vote comes just days after anti-austerity protests in the capital erupted in clashes that left 15 people injured, triggering fears that the economic crisis could push the normally placid Alpine nation of 2 million into instability.

Pahor pulled off an upset in the first round on November 11 when he won almost 40 per cent of the vote ahead of Turk, 60, with almost 36 per cent.

According to the latest opinion polls published on Friday, Pahor was expected to secure just 60 per cent ahead of 40 per cent for Turk.

Once seen as a star new member of the European Union, Slovenia is suffering one of the deepest recessions in the eurozone, while problems with its banks have raised alarm that it may need a bailout.

Slovenians fear the economic crisis could further push their placid nation of 2 million into instability.

Voting ends at 7 pm (1800 GMT) and exit poll results are expected shortly after that.

Source: Agencies