BERLIN: German prosecutors announced an investigation Tuesday into claims that Turkish agents are spying on alleged followers of exiled preacher Fethullah Gulen in Germany.

The probe came as a German state minister accused Turkey of the “unacceptable” espionage against supporters of Gulen, blamed by President Recep Tayyip Erdogan for a failed coup attempt last year. The claims open a new front in the diplomatic row between NATO allies Germany and Turkey, whose relationship has been strained by a series of disputes centred on human rights issues.

“It is clear that the Turkish secret service MIT is investigating people living in Germany,” said Boris Pistorius, interior minister of the northern German state of Lower Saxony, deploring the “intensity and ruthlessness” of Turkey s pursuit of people living abroad. “It’s intolerable and unacceptable,” he said at a press conference. Erdogan s government had asked Berlin to help spy on about 300 alleged Gulen supporters, Pistorius said, adding that the list was handed to German’ s BND spy service, which turned it over to state governments.

But Pistorius s state decided to inform the more than 10 targets in Lower Saxony, including a school and at least two companies, fearing people could suffer “retaliation” if they travelled to Turkey while unaware they were on a watch list. Turkish authorities were acting with “something close to paranoia,” he said, adding that “all Gulen supporters are assumed to be terrorists and enemies of the state even though there is not the tiniest scrap of evidence.” “As of today, we have no evidence whatsoever that Gulen supporters have violated any rules in any way.”

According to German media, Turkish officials handed the target list including names, addresses, telephone numbers and photographs to their German counterparts during the Munich Security Conference in February. Federal prosecutors will now examine how Turkey compiled such detailed information on their targets. “The success of our investigation will depend largely on the information shared with us by German counter-espionage agencies,” spokeswoman Frauke Koehler said about the probe into “persons unknown”.

Interior Minister Thomas de Maiziere meanwhile warned Turkey against spying in Germany, saying “espionage activities on German soil is punishable by law and will not be tolerated by us”.