The prisoners were being moved from a high-security facility in Al Taji, 15 miles north of Baghdad, to an unidentified prison.
According to Saad Maan, a spokesman for the Baghdad Military Operations Command, the militants attacked the convoy in order to free their imprisoned associates. "They had information the convoy would be moving, and they were targeting it."
At some point during the attack, he said, at least two militants blew themselves up, killing 44 prisoners.
Other reports put the death toll closer to 60 militants and eights Iraqi military members among the wounded.