At around 6am last Friday morning, seven men in plainclothes and two wearing simple vests identifying them as Turkish police officers banged on the front door of the Istanbul residence of Yigit Aksakoglu, 42, a consultant and civil society activist who gained a small measure of fame by taking part in anti-government protests more than five years ago.

Yigit Aksakoglu (Bernard Van Leer Foundation)

Mr Aksakoglu put on his clothes and said goodbye to his 7-year-old and his 2-and-a-half-year-old, who were in tears as he was hauled away.

“‘No, papa don’t go,’” his wife, Unzile, recalls her children crying out after him. “I told them, ‘They need your dad to do some work, but he will come back soon.’”

A week later, Mr Aksakoglu still has not come home. The London School of Economics graduate remains in jail, transferred to Istanbul’s Silivri Prison as the only person still locked up from among 14 scholars and civil society figures gathered up by Turkish authorities. They are accused of participating in an effort to overthrow the government five years ago, during the 2013 unrest over Gezi Park.

Many are baffled as to why, suddenly, Turkish authorities have chosen to resurrect tensions over the uprising at Gezi Park. The protest movement began over President Recep Tayyip Erdogan’s plans to develop green space in central Istanbul but soon mushroomed into broader protests across Turkey against the country’s leadership.

The new arrests have dampened hopes that Mr Erdogan would ease up on a widespread crackdown against political foes following his victory in general elections this year.

Authorities a year ago arrested businessman and philanthropist Osman Kavala, a prominent figure during the Gezi protests and chairman of an organisation called Anatolia Culture, which says it promotes cultural diversity and human rights.

Authorities have been holding Mr Kavala without charge for a year, and are now accusing Mr Aksakoglu and the others of being part of a broad foreign-backed conspiracy to topple the government during the Gezi protests.

“The person, who financed terrorists during the Gezi incidents, is currently in prison,” Mr Erdogan said this week in reference to Mr Kavala. “And who is behind him? The famous Hungarian Jew George Soros. This is a man who was assigned to divide nations and shatter them. He has so much money and he is spending it in these ways.”

There’s no evidence Mr Soros, a Hungarian-born banker and philanthropist, had anything to do with the Gezi protests. But Mr Kavala is an advisory board member of Mr Soros’ Open Society Foundation, which advocates the kind of non-violent civil disobedience tactics used by the Gezi protesters. Mr Soros has become a frequent target of leaders facing discontent across the world.

Protesters dance in Gezi park in 2013 (Reuters)

Mr Aksakoglu’s lawyer and advocates say his participation in the Gezi protests was never secret or conspiratorial. A fluent English speaker, he appeared frequently on international television broadcasts including BBC News and CNN and organised meetings discussing nonviolent action in public parks. Although he travelled in the same circles as Mr Kavala, he never met him, much less collaborated with him to overthrow the government, say his advocates.

Osman Kavala (Anadolu Kultur) (Anadolu Kultur)

Asli Kazan, a member of Mr Aksakoglu’s legal team, says the prosecutor has not yet given her the chance to confer with her client. She does not have access to the case file, but the indictment suggests the case was based on intercepted phone calls and other surveillance in the six months after the Gezi protests.

He is accused under an article of the Turkish legal code reserved for a violent attempt to overthrow the government, even though prosecutors acknowledge that he took part only in meetings to discuss non-violent protest.

“This investigation is really old,” says Ms Kazan. “The file was shelved at prosecutors office. It was a dead investigative file.”

The detentions risk damaging relations with Europe at a key moment when Turkey is seeking to smooth relations in an effort to restore investor confidence after months of financial turmoil. EU foreign policy chief Federica Mogherini discussed the issue in a tense moment in Ankara this week after her office issued a statement immediately following the arrests.

“Detentions of critical voices and the continued widespread pressure on civil society representatives run counter to the Turkish government’s declared commitment to human rights and to fundamental freedom,” it said.

Police fired teargas and water cannons at protesters in 2013 as they tried to prevent them gathering in Gezi Park (EPA)

Opponents of the government, including opposition leader Kemal Kilicdaroglu, have accused the government of trying to take “revenge” for Gezi by painting it as a coup attempt.

Some worry the arrests of people who had done little more than speak their minds marks yet another erosion of free expression in Turkey. Mr Erdogan has championed the cause of Saudi journalist Jamal Khashoggi even as human rights and press monitors have criticised declining Turkish media freedoms in the last few years.

“People will stay even more clear of gathering and speaking among themselves,” wrote Nevsin Mengu, a columnist for the leftist Evrensel newspaper.

But in recent years Mr Aksakoglu has been keeping his head down, like many activists of the Gezi era, focusing his efforts on his children and his work.

He now serves as an advocate for post-natal and toddler education as an employee of the Bernard Van Leer foundation.

“He broadly works on human rights and education and is rather effective,” says Emma Sinclair-Webb, of Human Rights Watch. “All of this innocuous activity is suddenly under scrutiny and being criminalised. This is just criminalising any sort of legitimate, human rights and civil society work even when it’s explicitly peaceful.”