SKOPJE (Reuters) - Macedonia’s state election commission said on Friday it had annulled ballots cast at a single polling station and ordered a new vote there after accepting that one woman had been prevented from voting in Sunday’s parliamentary election.

The re-run ballot at the polling station with just 800 voters in the western town of Gostivar could potentially change the result of the election, which veteran leader Nikola Gruevski won with the slimmest of majorities.

Ethnic Albanian party Besa had asked the election commission to overturn the result, saying the woman had not been allowed to vote because records erroneously showed she had already done so. Albanians, who make up about a third of the former Yugoslav republic’s 2.1 million people, form a majority in Gostivar.

State Election Commission chief Aleksandar Cicakovski said that appeal had been accepted and a fresh vote ordered.

Preliminary results of the snap vote on Sunday showed Gruevski’s VMRO-DPMNE winning 51 seats in Macedonia’s 120-seat parliament. The Social Democratic Union (SDSM) led by Zoran Zaev, Gruevski’s main rival, won 49 seats, helped by the first significant shift toward the party by Albanian voters since a 2001 inter-ethnic conflict.

Under Macedonia’s multi-seat constituency system, that change means the result in Gostivar - just one of 2,973 polling stations in which 1.19 million people voted on Sunday - could affect the final result of the election.

VMRO-DPMNE said it would appeal the electoral commission’s decision. The administrative court should decide whether to allow the appeal within 48 hours.

Up to a thousand VMRO-DPMNE supporters protested in front of the State Election Commission headquarters in Skopje on Thursday and Friday, claiming the party’s victory was being stolen by the opposition and commission officials.

The national election was called after Gruevski stepped down in January and handed over to a caretaker government following opposition allegations that he and his counterintelligence chief had tapped the phones of more than 20,000 people.

In an EU-brokered deal, both main parties agreed to hold early elections and appoint a special prosecutor to investigate the allegations which sparked a two-year-long national crisis.