A group of militants attending a suicide bombing training class north of Baghdad died when their instructor unwittingly set off an explosives belt during a a demonstration.
At least 21 militants were killed in the huge blast Monday that alerted authorities to the existence of the rural training camp. Nearly two dozen people were arrested, including wounded insurgents trying to hobble away from the scene.
The militants belonged to a network now known as the Islamic State of Iraq and the Levant, an extremist group that recently was disavowed by al-Qaida for not following orders.
The ISIL also has been known as the Islamic State of Iraq and Syria, or ISIS.
The militants are battling for control of mainly Sunni areas of western Iraq, in a key test of the Shiite-led government's ability to maintain security more than two years after the withdrawal of U.S. troops.