Chancellor Angela Merkel on Sunday warned Turkey not to "misuse" Interpol to pursue its critics after a Spanish court ordered the conditional release of a Turkish-German writer wanted by Ankara.
Dogan Akhanli, who writes about Turkey's human rights record, was arrested Saturday while on holiday in Granada on an Interpol red notice, similar to an international arrest warrant, from Ankara.
"That's not on," said Merkel about the latest case of a German citizen being pursued by President Recep Tayyip Erdogan's government, adding that countries "must not misuse international organisations such as Interpol".
Relations between Turkey and Germany, home to three million ethnic Turks, have been badly strained, particularly after the failed coup against Erdogan a year ago and a subsequent crackdown on alleged plotters, and the latest case threatens to further damage ties between the fellow NATO members.
Cologne-based Akhanli, who has previously been jailed in Turkey before being granted political asylum and citizenship in Germany, was released by the Spanish court on condition he stay in Madrid while authorities await the formal extradition request from Turkey.
German Foreign Minister Sigmar Gabriel also greeted the writer's release and said "it would be terrible if, even on the other side of Europe, Turkey succeeded in having people who raise their voices against President Erdogan arrested".
Merkel said it was "unfortunately one of many cases" of Turkey pursuing German citizens, mentioning Turkish-German journalist Deniz Yucel of the Die Welt newspaper, who faces trial on terror charges.
Such cases had led Germany to "massively change" its Turkey policy, Merkel said, speaking at a TV forum with voters, and referring to stepped up travel warnings and moves likely to dampen new investment in Turkey.
In Turkey, Erdogan called on Turkish-origin Germans to give a "slap" to both parties in Merkel's ruling coalition in September 24 elections.
Erdogan has caused consternation in Berlin by urging ethnic Turks in Germany to vote neither for Merkel's Christian Democratic Union (CDU) nor its coalition partner the Social Democratic Party (SPD) or the Greens.
Defiantly returning to the controversy for a third day in a row, Erdogan called on ethnic Turks to reject the "enemies of Turkey".
"Be with those who are friendly to Turkey. Don't worry if it's a small party, give them your vote. They will then grow and get bigger."
He did not specify which parties the Turkish community in Germany should consider voting for.
Gabriel, a senior member of the SPD, had bitterly denounced Erdogan's remarks as an "unprecedented act of interference" in Germany's sovereignty.
Merkel on Sunday said the tactic was "absolutely unacceptable".
Austria's Foreign Minister Sebastian Kurz also condemned "the constant interference by Erdogan in the internal affairs of other states".
"And it's not happening only in Germany," he told Die Welt am Sonntag newspaper.
German Green MPs have long taken up the cause of Akhanli, saying he is a victim of political persecution.
He was jailed in Turkey from 1985 to 1987 before moving to Cologne in the 1990s and becoming a German citizen in 2001.
Akhanli has written about the sensitive historical mass killing of Armenians under the Ottoman Turkish empire.
Half a million to 1.5 million Armenians were killed between 1915 and 1917, in a bloodletting that Armenia and Western historians describe as genocide.
Turkey vehemently objects to the term, saying that 300,000 to 500,000 Armenians and as many Turks died in civil strife when Armenians rose up and sided with invading Russian troops.
Akhanli was arrested again in 2010 when he arrived at Istanbul airport for a visit, on charges he was allegedly involved in a 1989 armed robbery, and held for four months.
He was released after being declared innocent, but an appeals court later ordered new proceedings against him.