Turkish President Recep Tayyip Erdogan called the arrested German newspaper reporter Deniz Yucel a "German agent," according to state-run news agency Anadolu, cranking up the tension between Ankara and Berlin amid already-fraught relations.
"As a representative of the PKK, as a German agent, this person was hiding for a month in the German consulate," Erdogan said on Friday in Istanbul at an award ceremony.
"We said for one month, give him to us, he needs to be brought before a court."
Relations between the two nations have been strained, in part over concerns about the scope of Turkey's crackdown in response to a failed coup attempt last July, and were aggravated when a Turkish court remanded Yucel in custody on Monday.
Protests have been held across Germany in support of Yucel, a dual German-Turkish citizen and Turkey correspondent for Die Welt newspaper.
Yucel has been accused by the Turkish authorities of spreading propaganda from the banned Kurdistan Workers' Party (PKK), as well as the movement of exiled cleric Fethullah Gulen, who Erdogan believes was the mastermind behind the military coup.
Yucel turned himself in at a police station in Istanbul last month, because Turkish authorities were searching for him.
Turkey has regularly complained to Germany for not handing terrorism suspects at the request of Istanbul.
Yucel is the first German journalist to have been detained as part of a sweeping purge of the media since the country announced a state of emergency following the attempted coup.
In the months since the July plot, the government has shuttered more than 150 government-critical media outlets. More than 120 journalists are in jail.
Yucel wrote a story for German newspaper Die Welt in September about the government's use of trolls on social media, based in part on emails that had been published by Wikileaks and a domestic group known as Red Hack.
The emails were apparently from the inbox of President Recep Tayyip Erdogan's son-in-law, Berat Albayrak, who is also the energy minister. Red Hack is considered a terrorist organization in Turkey.
All the information in Yucel's articles was in the public domain.