BERLIN (Reuters) - German Chancellor Angela Merkel criticized Turkey’s use of an Interpol arrest warrant to detain a German writer in Spain, telling an election town hall event on Sunday that this amounted to abuse of the international police agency.

Dogan Akhanli was stopped in Spain on Saturday after Ankara issued a “red notice”. The German-Turkish writer was released on Sunday but must remain in Madrid while Spain assesses Turkey’s extradition request.

“It is not right and I’m very glad that Spain has now released him,” Merkel said. “We must not misuse international organisations like Interpol for such purposes.”

Relations between Turkey and the European Union have been under growing strain since last year’s failed military coup in Turkey. European-Turkish nationals are among the 50,000 people detained since then in what critics condemn as an indiscriminate crackdown by President Recep Tayyip Erdogan.

Merkel has been more muted in her criticism of Erdogan than other German politicians, with critics charging her with being beholden to Erdogan because of Turkey’s role as a buffer against a renewed flood of Syrian war refugees arriving in Europe.

“(Dogan’s) is one of many cases, unfortunately,” Merkel said, in a sharpening of her tone toward Ankara. “That’s why we have massively changed our Turkish policy recently ... because it’s quite unacceptable that Erdogan does this.”

On Saturday Erdogan urged Turks in Germany to “teach a lesson” to Germany’s “anti-Turkish” mainstream parties in next month’s parliamentary election, despite German Foreign Minister Sigmar Gabriel’s warning he should keep out of German politics.

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“Who are you to talk to the president of Turkey? Talk to Turkey’s foreign minister. Know your place,” Erdogan said at a rally for his AK Party in the southwestern province of Denizli.

European countries with large Turkish diasporas have grown increasingly uneasy at what they see as Ankara’s attempts to use ethnic Turkish populations to influence domestic politics.

“President Erdogan is trying to instrumentalise ethnic Turkish communities, especially in German and Austria,” Austrian Foreign Minister Sebastian Kurz told Die Welt newspaper. “He polarises and brings Turkish conflicts into the EU.”

The final days before elections in the Netherlands this year were overshadowed by violent protests by local affiliates of Erdogan’s party. German security officials have expressed concern about a possible repetition in Germany.

Interpol did not immediately respond to a request for comment on Merkel’s remarks.