Turkish police arrested the chairman of Amnesty International Turkey on Tuesday, on charges of collusion with exiled imam Fethullah Gülen, alleged mastermind behind the failed coup attempt of July 2016.

Taner Kiliç was taken from his home in Izmir by police at 6:30am Tuesday morning. At the same time, security forces arrested 22 other lawyers accused of having ties with the movement headed by Gülen, who has been living in exile in Pennsylvania.

Police searched Kiliç’s home and office, but at the moment it doesn’t appear that they suspect illicit connections with Amnesty International itself.

In a statement, Amnesty International’s Secretary General Salil Shetty, denounced the arrest as part of a “post-coup purge” by the Erdogan government.

“The fact that Turkey’s post-coup purge has now dragged the Chair of Amnesty International Turkey into its web is further proof of just how far it has gone and just how arbitrary it has become,” Shetty said. “Taner Kiliç has a long and distinguished record of defending exactly the kind of freedoms that the Turkish authorities are now intent on trampling.”

“In the absence of credible and admissible evidence of their involvement in internationally recognized crimes,” Shetty added, “we are calling on the Turkish authorities to immediately release Taner Kiliç along with the other 22 lawyers, and drop all charges against them.”

Taner Kiliç has served on the board of Amnesty International Turkey for various periods of time since 2002 and was elected chairman in 2014.

“In the course of decades of activity in favor of human rights within Turkish human rights organizations, he has always been recognized for his unremitting efforts in favor of human rights,” said Amnesty Italy.

He was also one of the lawyers who followed the story of Gabriele Del Grande, an Italian journalist detained by Turkish police near the border with Syria and released after fourteen days.

Tuesday’s arrests are part of a broader investigation of alleged members of the so-called “Gülenist Terror Organization.” U.S. security officials reportedly do not believe that Gülen is involved in terrorist activities.

Since the coup attempt, Turkish authorities have arrested some 50,000 people and fired or suspended 150,000 government employees, including soldiers, police officers, teachers and public servants, for alleged links to Gülen’s movement and other groups.

Follow Thomas D. Williams on Twitter