VIENNA (Reuters) - Austria called on Turkey on Wednesday to immediately explain why one of its nationals, a student and activist who writes for a far-left website, has been arrested in Ankara.

Max Zirngast, a political science student in his late 20s who writes for online publication Re:volt, has been held since Tuesday morning. Re:volt has said it believes the allegation against him is membership of a terrorist organization and that any such charge would be false.

“We expect Turkey to immediately explain what the journalist is accused of, and if that is not possible then to immediately release him,” Austrian Chancellor Sebastian Kurz told reporters before a weekly cabinet meeting.

Kurz’s government, a coalition of his conservatives and the anti-immigration Freedom Party, is opposed to Turkey joining the European Union and has called for accession talks to be broken off. However, both countries have recently tried to improve their relations.

Part of the reason for Austria’s hard line has been Ankara’s crackdown following a failed coup attempt in July 2016 that Turkey says was orchestrated by a U.S.-based cleric who was once a close ally of President Tayyip Erdogan.

Turkey has detained around 160,000 people, including many journalists, and dismissed nearly the same number of civil servants since the putsch attempt, the U.N. human rights office said in March. Of that number, more than 50,000 have been formally charged and kept in jail during their trials.