German authorities are investigating 20 Turkish citizens on suspicion of conducting espionage in Germany, a newspaper reported on Thursday.

Die Welt said it received the information in an official government response to a question about the issue filed by Sevim Dagdelen, a German lawmaker with the hard left party Die Linke.

Tensions are running high between the two NATO allies ahead of a referendum in Turkey next month that proposes expanding the powers of President Tayyip Erdogan. Berlin infuriated Ankara after cancelling several campaign rallies by Turkish ministers in Germany, drawing accusations from Turkey of “Nazi” tactics.

Germany’s Federal Prosecutor’s Office (GBA) said last month it had launched a probe into suspected spying by Turkey.

Source: Websites