BRUSSELS (AP) — The European Union's executive arm has expressed regrets after its top official threw her support behind the ruling conservative party in Croatia's parliamentary elections.

Ursula von der Leyen, the German president of the European Commission, appeared with other center-right politicians in a promotional video clip posted by the Croatian Democratic Union (HDZ) ahead of Sunday's vote, in breach of political neutrality guidelines for commission officials.

A former defense minister in Germany, Von der Leyen is a member of the center-right Christian Democratic Union (CDU) and belongs to the same European People’s Party as HDZ.

The code of conduct for members of the European Commission states that they “shall abstain from making public statements or interventions on behalf of any political party or organization of the social partners of which they are members," except when they stand for election or participate in a vote.

Reacting to the avalanche of criticism on social media, the chief spokesman for the commission, Eric Mamer, said Von der Leyen weighed in the Croatian campaign in “her personal capacity."

“Regrettably, this was not made clear in the final version of the video," Mamer said on Sunday.

Von der Leyen was identified as the European Commission president in the video and was filmed standing in front of a European flag.

According to partial results, the ruling conservatives overwhelmingly won the elections held Sunday. With over 90 percent of the vote counted, the HDZ has 66 seats in Croatia’s 151-seat parliament and is likely to form a new coalition government with smaller right-wing groups.