The suspects were held on Friday in dawn raids across Turkey in an operation focused on the offices and homes of members of the Peace and Democracy Party (BDP), the main party in parliament representing Turkey’s restive Kurdish minority.

The BDP, which formed a bloc of 29 deputies in the national assembly, has accused the government of trying to neutralize opponents before planned constitutional reforms, which are expected to include the question of Kurdish rights.

A total of 38 people had been detained and prosecutors asked for 35 of them to be remanded in custody. The court set four of them free, broadcaster CNN Turk reported.

Among those remanded was former BDP deputy Fatma Kurtulan and a one-time leader of the former Kurdish party DEHAP, Tuncer Bakirhan, it said. Nobody was available at the court to confirm the reports and the specific charges were unclear.

Kurds make up about 15 percent of the country’s 74 million population. BDP officials say up to 5,000 BDP members, including elected mayors and provincial leaders in the mainly Kurdish southeast have been detained.

The probe, closely watched by the European Union, which Turkey hopes to join, centers on an organization called the Union of Kurdistan Communities (KCK).

According to a 2009 indictment, the Kurdistan Workers Party (PKK), a rebel group branded a terrorist organization by Ankara, the EU and the United States, established the KCK with the aim of creating its own Kurdish political system.

Some 150 politicians and activists are already being tried in Diyarbakir, where a large courtroom has been specially built, on charges of membership of an armed terrorist group. Similar trials are being held in other cities across Turkey.

More than 40,000 people have been killed in the conflict between the PKK and the state since the militants launched their armed insurgency in 1984.