Berlin (CNN)It was the evening of July 5 and Magdalena Freudenschuss hadn't heard from her partner all day. That was unusual, so she was worried.
Turkey arrests 'threaten everyone,' says partner of detained German activist
Peter Steudtner, a human rights trainer, was at a workshop on IT security and mental health strategies for activists in Istanbul with several colleagues.
"We made calls to Turkey to find out what had happened, whether it was just an internet problem," Freudenschuss told CNN. "And then we found out through the consulate."
Steudtner had been detained along with another trainer and eight human rights activists, including the director of Amnesty International in Turkey, Idil Eser.
Three weeks later, all of them -- now known as the "Istanbul 10" -- remain in custody, accused by Turkish authorities of "committing crimes in the name of a terrorist organization without being a member."
Freudenschuss was allowed a brief phone call with Steudtner soon after his arrest, but "he couldn't tell me a lot," she said. "At that point we didn't foresee how long it would take."
At first, Steudtner and the others were kept in solitary confinement, but they have since been put together in one cell, Freudenschuss said.
He has started a yoga routine and leads his cellmates in classes, according to Freudenschuss' family representative.
But Freudenschuss knows little else about the conditions in which Steudtner is living, and can contact him only via messages passed on by his lawyer.
Freudenschuss and Steudtner, who live in Berlin and have been together for 10 years, have two children together.
"It's hard for them as well," she said. "There is a father missing, there's someone missing who reads books to them, who listens to me, to the kids."
The Turkish government has not responded to CNN's request for comment. But presidential spokesman Ibrahim Kalin last week defended the decision to detain the activists.
"They are people who according to the police and the judiciary are engaged in illegal or suspect actions," said Kalin, who called for Germany to "respect Turkey's judicial independence."
The allegations against the activists are "unjustified and obscure," said Markus Beeko, secretary general at Amnesty International in Germany told CNN.
"The Turkish authorities have used absurd allegations to try to justify this breach of international human rights standards," he said.
The arrests came just a month after the detention of Taner Kilic, Amnesty's Turkey chair, was charged with "membership of the Fethullah Gulen Terrorist Organisation" -- the name given to followers of the exiled cleric Fethullah Gulen, who Turkey's government believes was behind last year's attempted coup. Gulen has denied involvement in the coup attempt.
"The two top representatives of Amnesty in Turkey are now detained and this is a first in the 56-year-history of Amnesty International," Beeko said.
Freudenschuss is concerned about the wider implications of the arrests.
"Of course it's something very personal for me, but it's also something which is a danger for human rights defenders everywhere in the world," she said.
"It's really an issue beyond these 10 people being charged with something they didn't do. There's more at stake if independent human rights trainers cannot go somewhere and support human rights defenders," she added. "I think it's a threat for everyone."
On Tuesday, protesters gathered outside European Parliament in Brussels -- where EU foreign policy chief Federica Mogherini met Turkish Foreign Minister Mevlut Cavusoglu -- to call for the release of the activists.
Statements given by Mogherini and Cavusoglu after the meeting suggested little progress had been made.
German Foreign Minister Sigmar Gabriel said Monday that efforts to gain access to the activist thus far had been unsuccessful.
In a press conference last week, Gabriel called for Steudtner's release and had strong words for Turkish President Recep Tayyip Erdogan.
"What is happening in Turkey is blatantly obvious," he said. "Someone who detains law-abiding visitors to their country on the basis of outlandish, indeed absurd, accusations and throws them into prison has left European values behind," he said.
In the wake of last year's coup attempt, Erdogan has tightened his grip on power while overseeing a massive purge of those who he says rose up against him.
Over the past 12 months his government has clamped down on civil liberties across Turkey, gutted public institutions and universities, heavily restricted the media and ordered mass arrests.
More than 169,000 people have faced "judicial action" ranging from travel restrictions and detentions to arrest warrants since the coup attempt, according to the justice ministry, the state news agency Anadolu reported.