Austria's highest court is due to rule on whether presidential elections narrowly lost by a right-wing candidate must be repeated after his party claimed gross irregularities in the absentee vote count.

Freedom Party candidate Norbert Hofer was leading after polls closed May 22. But final results after a count of absentee ballots put former Green party politician Alexander Van der Bellen ahead by only a little more than 30,000 votes.

The final count showed Van der Bellen with 50.3 percent, compared with 49.7 percent for Hofer.

The Freedom Party says the law was contravened in one way or another in most of the 117 electoral districts, including the sorting of absentee ballots before electoral commission officials arrived.

The ruling is expected at noon local time (1000 GMT) Friday.