Turkish police Friday detained over a dozen people, including academics, with links to an association led by jailed human rights activist Osman Kavala, a state-run news agency reported.
Police issued arrest warrants for 20 people as part of an investigation into Anadolu Kultur (Anatolian Culture), whose chairman Kavala has been jailed for more than a year without having been formally charged, Anadolu news agency said.
Thirteen were rounded up early Friday in simultaneous raids at various addresses that included Istanbul, Mugla in the southwest, and Adana and Antalya in southern Turkey, it added.
Two Istanbul professors -- Betul Tanbay of the prestigious Bogazici University and Turgut Tarhanli, deputy dean of the private Bilgi University -- were among the detainees.
The operation also targeted Anadolu Kultur executives, including deputy chairman Yigit Ekmekci, board member Ali Hakan Altinay, coordinator Asena Gunal, and consultants Meltem Aslan and Cigdem Mater, the agency said.
Mater is also a journalist.
The individuals are suspected of "creating chaos and mayhem" and "seeking to overthrow the government," Anadolu reported.
They are alleged to have invited "facilitators and professional activists" to back 2013 anti-government protests, and to have called for a ban on the importation of tear gas to Turkey.
Kavala, a philanthropist and co-founder of the Iletisim publishing house, is well-known in intellectual circles in Turkey and abroad.
He is accused of "attempting to remove the constitutional order" and "attempting to overthrow the government", but has not been charged with a crime.
According to his lawyers, Turkish authorities suspect him of having links to a failed 2016 coup attempt, and of financing anti-government demonstrations during the 2013 protest movement.
Kavala was arrested on October 18, 2017, and remanded in custody the following month.
- 'Brutal assault'-
Opposition CHP party MP Sezgin Tanrikulu criticised the arrests on Twitter.
"Again a Friday, again detentions... Those who expect normalisation from this regime should continue to dream," he said, referring to President Recep Tayyip Erdogan's ruling Justice and Development Party (AKP).
Kati Piri, European Parliament's Turkey rapporteur, also blasted the arrests as "another brutal assault on Turkish civil society," while the Council of Europe expressed concern.
"EU must strongly condemn!" Piri tweeted.
Thorbjorn Jagland, secretary general of the Council of Europe that monitors democracy and human rights, said in a statement he would raise "this alarming development with the Turkish government as a matter of urgency."
Amnesty International said the arrests showed "how desperate Turkish authorities are to crack down on any form of dissent."
It added in a statement: "This latest wave of detentions of academics and activists, on the basis of absurd allegations, shows that the authorities are intent on continuing their brutal crackdown of independent civil society, and shatters any illusion that Turkey is normalising following the lifting of the state of emergency."
Kavala's Anadolu Kultur NGO, which aims to overcome differences within Turkish society through culture and the arts, has sought to reach out to neighbouring Armenia.
Ankara has no diplomatic relations with Armenia, partly due to the dispute over the mass killings of Armenians under the Ottoman Empire which Yerevan considers a genocide.
Kavala, who has urged for the killings to be recognised as genocide, is regularly compared by pro-government Turkish media to liberal US billionaire George Soros.
Turkish authorities have launched a mass crackdown and arrested more than 50,000 people over alleged links to the plotters of the 2016 coup attempt.