A gang of 21 Iraqi militants accidentally set off their own car bomb as they were making a promotional propaganda video about a would be suicide bomber.
The explosion left all 21 dead and resulted in two dozen arrests at the camp outside Samarra, a Sunni city 95 kilometers (60 miles) north of Baghdad, Iraqi officials said.
In the city of Mosul to the north, meanwhile, the speaker of parliament - one of the most prominent Sunni officials in Iraq - escaped unhurt from a roadside bomb attack on his motorcade.
A police officer said the militants were attending a lesson on making car bombs and explosive belts when a glitch set off one of the devices.
The officer said security forces rushed to the area after hearing the sound of the explosion. They arrested 12 wounded suspected militants plus another 10 trying to flee the area.
Medical officials confirmed the casualties. All officials spoke anonymously because they were not authorized to speak to media.
Violence has spiked in Iraq since April of last year. Militant groups regularly stage coordinated car bomb attacks in the capital.
Security forces found seven car bombs, several explosive belts and roadside bombs after searching two houses and a garage in the orchard, he said.
