BAGHDAD (AP) — An instructor teaching his militant recruits how to make car bombs accidentally set off explosives in his demonstration Monday, killing 21 of them in a huge blast that alerted authorities to the existence of the rural training camp in an orchard north of Baghdad. Nearly two dozen people were arrested, including wounded insurgents trying to hobble away from the scene.

The fatal goof by the al-Qaida breakaway group that dominates the Sunni insurgency in Iraq happened on the same day that the speaker of the Iraqi parliament, a prominent Sunni whom the militants consider a traitor, escaped unhurt from a roadside bomb attack on his motorcade in the northern city of Mosul.