A 26-year-old German ex-jihadi says he plans to reveal details about the inner workings of the Islamic State group "so that the world knows the truth."

Ebrahim H. B. went on trial Monday alongside 27-year-old Ayoub B. charged with membership of a terrorist organization.

The two German-Tunisian citizens, whose surnames weren't released due to German privacy rules, allegedly traveled to Syria last year to join IS. They returned to Germany last August and September.

Prosecutors say H.B. volunteered for a suicide bombing in Iraq but the attempt was aborted.

Ahead of the trial in the northern city of Celle, H.B. told public broadcaster NDR that IS recruits are given the option of fighting or carrying out suicide bombings, and that he would prefer prison in Germany to freedom in Syria.