Germany’s domestic security agency has turned its attention to the Turkish-Islamic Union for Religious Affairs (DİTİB), one of Germany’s largest Islamic organisations, after reports of unconstitutional nationalist and religious activities at the union’s mosques.

The Federal Office for the Protection of the Constitution presented documents and data on DİTİB with German federal state authorities after reports that Turkey’s military operations in northwest Syria this year had sparked unconstitutional activities and speeches among DİTİB congregations, German state broadcaster Deutsche Welle reported on Thursday.

The security agency had prepared the documents on DİTİB to decide on whether intelligence services should monitor the union for unconstitutional activities.

The Islamic union, which was set up in 1984 as a branch of Turkey’s Directorate of Religious Affairs (Diyanet), funds around 900 mosques in Germany and boasts a membership of around 800,000. While DİTİB says it is not officially linked to the Turkish state, it has been accused of spying for Turkey on German citizens, resulting in a temporary suspension of federal funding in 2017.

“DİTİB is not a religious organisation,” Deutsche Welle quoted Burkhard Freier, head of the Federal Office for the Protection of the Constitution in North Rhine Westphalia. Freier added that the union had been monitored by German intelligence for Turkish nationalist activities in the past.

The files shared with federal authorities reportedly included a report stating that DİTİB Nevzat Yaşar Aşıkoğlu worked with Turkey’s Berlin embassy, and that he had been chosen by Turkey’s Diyanet, and not by the union’s members in Germany.

Investigations by the Federal Office for the Protection of the Constitution in North Rhine Westphalia had found that DİTİB imams had reported 28 Turkish dissidents to the embassy, Deutsche Welle said. The union has also reportedly kept the Turkish embassy informed on a number of associations said to be linked to the Gülen movement, which Turkey says planned the July 2016 coup attempt.

Despite this, one German security official quoted by Deutsche Welle said there was no evidence DİTİB had engaged in destructive or expansionist activities in Germany.

The report added that, while the union’s Turkish nationalism had been noted, it was not engaged in radical religious activities. This meant that “serious legal obstacles” would have to be surmounted for the intelligence services to begin investigating whether DİTİB had breached the constitution, said an interior ministry spokesperson.