The investigation, announced on Monday, is looking into whether Osman Ozcelik, Aysel Tugluk and Fatma Kurtulan had contact with or links to the PKK. All three are deputies of the Democratic Society Party (DTP) who travelled to northern Iraq last week to try and negotiate the release of eight Turkish soldiers captured by the PKK in the south eastern province of Hakkari on October 22. All eight were released on Sunday.
The prosecutors office is investigating whether the three deputies breeched Turkeys Anti-Terror Law and Turkish Penal Code by having contact with a terrorist organisation.
Koksal Toptan, the speaker of the Turkish parliament, said on Monday that the trip and activities of the three DTP deputies had been a private act and not sanctioned by the state.