Germany has rejected a formal request from Turkey to freeze assets of members of the network of US-based cleric Fethullah Gulen, Germany’s Spiegel magazine reported on Saturday.

Without naming its sources, the magazine said the Turkish government had asked the Foreign Ministry in Berlin at the end of April to freeze the assets of the Gulen organization and its members in Germany. It attached a list with 80 names, it said.

Gulen is believed to be the chief architect behind last year’s failed coup in Turkey.

The move is likely to worsen already strained ties between the two NATO allies after Chancellor Angela Merkel said on Friday Germany should react decisively to Turkey’s detention of two more German citizens on political charges.

The German government officially rejected the request at the end of June, telling Ankara there were no legal grounds for Germany’s financial watchdog BaFin to crack down on the Gulen movement and its supporters, the report said.

The report also said that the number of Turkish extradition requests sent to Germany had jumped to 53 since the beginning of the year, already exceeding the total in the whole of 2016.

Turkey’s private Dogan news agency said Turkish authorities had detained two German nationals on Thursday over suspected links to last year’s failed coup attempt.

Dogan said the two German citizens of Turkish origin were detained at the Antalya airport, a popular Mediterranean tourist destination, over alleged links to the Gulen organization.

Turkish officials were not immediately available for comment, with the celebrations for the Muslim festival of Eid causing delays in contacting officials.

Twelve German citizens are now in Turkish detention on political charges, four of them holding dual citizenship. Among these is German-Turkish journalist Deniz Yucel, who will have been in detention 200 days on Friday.