He said: "Al-Qaeda's agenda started to reveal itself clearly in October last year ... they started to consider themselves as a state and started to target other Iraqi resistance factions, including prominent Sunni personnel in our community, and this affected our relations with them.
"These killings started a media war between them and us, so we decided to break away quickly in order not to give our enemies the chance to benefit from it."
The Islamic Army in Iraq is thought to be the largest armed group and was established during the summer of 2003 to fight coalition forces.
When first formed, the group appeared to have the same ideologies as al-Qaeda the group has said its primary focus was the expulsion of foreign troops from Iraq.
The group claims it is composed primarily of Iraqis (Sunnis, Shias, and Kurds) as well as Arabs.