German-Turkish author Dogan Akhanli was arrested in Spain on Saturday after Turkey issued an Interpol warrant for the writer, a critic of President Recep Tayyip Erdogan's government, fanning an already fierce row between the NATO allies, reported Reuters.

The arrest of the German national in Granada was part of a "targeted hunt against critics of the Turkish government living abroad in Europe," Akhanli's lawyer Ilias Uyar told magazine Der Spiegel, which first reported Akhanli's detention.

A German foreign office official said Germany was in touch with Spanish authorities demanding that Berlin be involved in any extradition proceedings and insisting that no extradition should take place.

Any country can issue an Interpol "red notice", but extradition by Spain would only follow if Ankara could convince Spanish courts it had a real case against him.

"This is a development of dramatic significance," said Social Democrat leader Martin Schulz at a campaign rally. "As part of his (Erdogan's) paranoid counter-putsch, he is reaching out for our citizens on the territory of European Union states."

Schulz, who seeks to replace Chancellor Angela Merkel in elections on Sept. 24, called for talks on Turkey joining the EU's customs union to be suspended, saying that Erdogan was "every day testing the limits of how far he can go."

The German Journalists' Union warned journalists critical of Ankara to have German police check their Interpol records before traveling abroad.

"To our knowledge, our colleague has done nothing wrong," said Frank Ueberall, the union's president.

Merkel has been cautious in her criticism of Erdogan despite Ankara's arrests of Germnan citizens. Critics say she is beholden to him because Turkey stands in the way of another wave of Syrian war refugees arriving in Europe, as they did in 2015, endangering her politically.

On Friday, Erdogan urged the three million or so people of Turkish background living in Germany to "teach a lesson" to Germany's main parties by boycotting them in the elections.