The trial of 47 men charged with terrorism has begun in the western Kazakh city of Aqtau.
The suspects, aged between 21 and 32, are charged with creating a terrorist group and preparing or carrying out explosions in the city of Atyrau and other towns in the region.
It is not clear how many of the 47 suspects have been detained by the authorities, and officials have said some of them are being tried in absentia.
The trial, in the provincial capital, is not open to the public.
The suspects were arrested after two explosions in Atyrau in October 2011.
One suspected suicide bomber was killed.
A group called Jund al-Khilafah (Soldiers of the Caliphate), a "brigade" of Islamist fighters based on the Afghan-Pakistani border, claimed credit for the bombings in a statement released on jihadist forums.
With Kazinform and RFE/RL's Kazakh Service reporting