BAGHDAD, April 8 (UPI) -- U.S. officials say Iraq's security is being tested mainly by Shiite militias using deadly attacks at higher rates than other militias.
U.S. military information shows targeted assassinations are the leading method of the insurgency, The Washington Post reports.
Shiite gunman killing Sunnis make up the bulk of the assassinations.
The militias are all linked to political factions of some sort.
The most deadly is the Badr Organization, part of the Iranian-backed Supreme Council for the Islamic Revolution of Iraq and the Mahdi Army, loyal to cleric Moqtada Sadr.
The two groups don't necessarily get along but make up the leading bloc of Iraq's Parliament.
Maj. Gen. Joseph Peterson said the United States has asked the Iraqi government to clean out the militias.
The Ministry of the Interior, specifically, has been accused of allowing Shiite militias to operate within its fold.
Sunni militias like al-Qaida in Iraq and Ansar al-Sunna are also blamed for attacking civilians and U.S. and Iraqi soldiers.
Kurdish militias, like the Peshmerga, are seen to operate in the north of Iraq and aren't considered a threat.
