BERLIN (Reuters) - Germany will not tolerate Turkish intelligence operations within its borders, the head of the country’s domestic spy agency said on Thursday after its chief prosecutor launched an investigation into possible spying by Turkish clerics.

Hans-Georg Maassen, Germany's head of the German Federal Office for the Protection of the Constitution (Bundesamt fuer Verfassungsschutz) addresses a news conference to introduce the agency's 2015 report on threats to the constitution in Berlin, Germany, June 28, 2016. REUTERS/Fabrizio Bensch - RTX2IODR

Hans-Georg Maassen said Berlin was very concerned about recent developments in Turkey, as well as “influence operations” directed against the Turkish minority in Germany or Germans with a Turkish migration background.

“We cannot accept that intelligence agencies are operating in Germany against German interests, and that is why we protest,” Maassen told reporters in Berlin.

The investigation, begun this week, followed a criminal complaint filed in early December by Volker Beck, a German lawmaker and religious spokesman for the Green party.

The issue threatens to further strain ties between NATO partners Germany and Turkey.

Ankara has accused Berlin of harboring militants from the Kurdistan Workers Party (PKK) and far-leftists of the DHKP-C, which has carried out attacks in Turkey. German officials reject that claim.

In June the German parliament voted in June to declare the 1915 massacre of Armenians by Ottoman forces a genocide, and Berlin has criticized a security clampdown by Turkish authorities since a failed coup in mid-July.

Beck said he filed his complaint after reports that Ankara had asked Muslim imams sent from Turkey to work for Ditib, Germany’s largest association of mosques, to provide information about followers of U.S.-based cleric Fetullah Gulen.

Turkey’s President Tayyip Erdogan accuses Gulen of masterminding the unsuccessful putsch.

The Green lawmaker criticized the prosecutor’s office for waiting so long to launch an investigation, and said it was unclear if possible suspects had left the country.

A spokesman for the prosecutor’s office said the probe was directed against unknown perpetrators because there was not yet sufficient evidence to target specific individuals.

German police last month arrested a 31-year-old Turkish man suspected of providing information on Kurds living in Germany to Turkish intelligence agencies.

Bekir Alboga, general secretary of Ditib, was quoted in the Rheinische Post newspaper last week as saying that some Ditib imams had mistakenly provided information about Gulen followers to Turkish religious affairs directorate Diyanet.

But in a statement on the Ditib website dated Jan 12, Alboga said he had not confirmed reports of spying. He said initial instructions to clerics from Diyanet were confusing, but the agency had clarified last month that imams were only expected to carry out religious duties.

“We are taking the charges seriously and investigating them ourselves,” Alboga said.