Austrian presidential candidate Alexander Van der Bellen, who is supported by the Greens, addresses a news conference in Vienna, Austria, September 12, 2016. REUTERS/Leonhard Foeger

VIENNA (Reuters) - Independent candidate Alexander Van der Bellen is catching up against his far-right rival in a Gallup poll ahead of December’s repeat election for the Austrian presidency.

The anti-migrant Freedom Party’s candidate Norbert Hofer has been seen in the lead since Austria’s highest court annulled the result of a May run-off - which Hofer narrowly lost - due to irregularities in the counting of postal ballots.

A series of Islamist attacks in Europe and Britain’s decision to leave the European Union since the original vote have made security concerns and the debate about Austria’s role in the bloc dominant campaign themes.

The poll of 800 people published by the Oesterreich paper on Sunday showed the midpoint of the wide range of support for former Greens leader Van der Bellen at 49 percent -- two points higher than a poll in August found -- versus 51 percent for the anti-migrant Freedom Party’s candidate Hofer.

The repeat election date was postponed to Dec. 4 earlier this week due to problems with non-sticking glue on ballots.

The poll, carried out from Tuesday to Thursday, also showed the Austrians’ continued strong support for the eurosceptic Freedom Party (FPO).

Asked which party they would vote for at parliamentary elections, 35 percent of the respondents chose the FPO. The governing coalition parties lagged far behind: the Social Democrats at 26 percent and the conservative People’s Party at 19 percent.