Turkey on Sunday accused Germany of supporting the network of a U.S.-based Muslim cleric it blames for last year's attempted coup, comments likely to aggravate a diplomatic feud between Ankara and Berlin.
On Saturday, German news magazine Der Spiegel published an interview with the head of the BND foreign intelligence agency, who said Ankara had failed to convince it that the cleric Fethullah Gulen was responsible for the coup attempt.
"Turkey has tried to convince us of that at every level but so far it has not succeeded," Bruno Kahl was quoted as saying.
President Tayyip Erdogan's spokesman said Kahl's comments were proof Germany was supporting Gulen's network, which Ankara refers to as the "Gulenist Terrorist Organisation" or "FETO".
"It's an effort to invalidate all the information we have given them on FETO. It's a sign of their support for FETO," Ibrahim Kalin told broadcaster CNN Turk.
"Why are they protecting them? Because these are useful instruments for Germany to use against Turkey."
Germany and Turkey have been locked in a deepening row after Berlin banned some Turkish ministers from speaking to rallies of expatriate Turks ahead of a referendum next month, citing public safety concerns.
Kalin said there was a possibility Erdogan could plan a rally to address Turks in Germany before the April 16 referendum on changing the constitution, a move that would further heighten tensions with Berlin.
The constitutional change would give Erdogan sweeping new powers. Critics say it would give him too much power.
The Turkish government blames Gulen's network of followers in the military for the abortive putsch in July, when a group of rogue soldiers seized tanks, helicopters and war planes to attack parliament and attempt to overthrow the government. More than 240 people died in the attempt.
Gulen, a former Erdogan ally who has lived in self-imposed exile in the United States since 1999, has denied the charges and condemned the coup.