An explosion Monday near Baghdad left about 20 people dead and another 15 or so wounded, according to news reports.
None of those killed, it appears, were innocent victims or Iraqi security personnel.
Instead, insurgents reportedly "set off their own car bomb at a training camp in an orchard," The Associated Press reports.
According to The New York Times, army and police officials believe the insurgents' commander "unwittingly conducted a demonstration with a belt that was packed with explosives."
The Times says the militants "belonged to a group known as the Islamic State of Iraq and Syria, or ISIS, which is fighting the Shiite-dominated army of the Iraqi government, mostly in Anbar Province. But they are also linked to bomb attacks elsewhere and other fighting that has thrown Iraq deeper into sectarian violence."
The AP refers to the group as the "Islamic State of Iraq and the Levant, an extremist Sunni group that recently broke with al-Qaida." We wrote last week about al-Qaida leader Ayman al-Zawahiri's statement distancing his organization from those militants in Iraq and Syria.
According to the AP, at the scene Monday authorities found "seven car bombs ... several explosive belts and roadside bombs after searching two houses and a garage in the dense area."
Reports vary on how many, but a number of alleged militants were arrested at the scene, officials say.