A total of 38 people had been detained and prosecutors asked for 35 of them to be remanded in custody. The İstanbul 14th High Criminal Court set four of them free and ruled to arrest
Kurtulan and the leader of the now defunct pro-Kurdish Democratic People's Party (DEHAP), Tuncer Bakırhan, are among those arrested.
The suspects were all held on Friday in dawn raids across Turkey in an operation focused on the offices and homes of members of the BDP.
Turkish police have recently stepped up operations against the KCK. The KCK investigation started in December 2009 and a large number of Kurdish politicians, including several mayors from the pro-Kurdish BDP, have been detained.
The suspects are accused of various crimes, including membership in a terrorist organization, aiding and abetting a terrorist organization and attempting to destroy the country's unity and integrity. BDP officials have said the investigation is the government's method of suppressing the BDP politicians, denying any links between the suspects and any terrorist organizations.