BERLIN (Reuters) - Germany launched a second investigation on Tuesday into suspected spying by Turkey and its interior minister said Berlin would not tolerate foreign espionage on its soil.

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 by cancelling several campaign rallies by Turkish ministers on German soil, drawing accusations from Turkey of “Nazi” tactics.

Media reports of Turkish espionage targeting members of Germany’s large ethnic Turkish diaspora have deepened the rift.

“We have launched an investigation against an unnamed entity on suspicion of espionage,” a spokesman for the Federal Prosecutor’s Office (GBA) said.

He declined to comment on German media reports that the entity was the Turkish Intelligence Agency (MIT) and that it was suspected of spying on supporters of U.S.-based cleric Fethullah Gulen. Ankara accuses Gulen of organizing a failed coup last July, a charge he denies.

A GBA spokeswoman said the investigation was separate from a probe launched earlier this year into possible spying by clerics sent to Germany by the Turkish government.

“Both cases concern suspected espionage involving Turkey, but at this moment there is no common substance to the two probes,” she said.

There was no immediate response from Turkish officials.

LIST OF NAMES

The Sueddeutsche Zeitung newspaper and two broadcasters have reported that Turkish intelligence gave Germany’s foreign intelligence service a list of names of more than 300 supposed Gulen supporters living in Germany and 200 groups, schools and other institutions associated with the cleric.

A German investigation indicated some of the photos may have been taken by hidden surveillance cameras, the reports said.

One German government source said it was clear that there was spying involved because of the nature of the documents provided to Berlin by the Turkish government.

Interior Minster Thomas de Maiziere said on Tuesday he was not surprised by the latest media report and that the lists of names would be looked at individually.

“We have told Turkey several times that such (activity) is not acceptable. Regardless of what you think of the Gulen movement, German law applies here and citizens who live here won’t be spied on by foreign states,” he said.

Since last year’s abortive coup Turkish authorities have purged state institutions, schools, universities and media of tens of thousands of Gulen’s suspected supporters, prompting concerns in the European Union about human rights abuses.

German and EU officials also fear victory for Erdogan in the April 16 referendum will further stifle dissent and undermine democracy in Turkey.

The speaker of the Bundestag lower house of parliament said in a speech late on Monday that Turkey was turning into an authoritarian system and that its president was effectively staging a coup against his own country.

Norbert Lammert, a member of Chancellor Angela Merkel’s conservatives, said the referendum was about “transforming an undoubtedly fragile but democratic system into an authoritarian system - and this second coup attempt may well be successful”.