BAGHDAD, Iraq (AP) - The Iraq insurgency is far larger than the 5,000 guerrillas previously thought to be at its core, U.S. military officials say, and it's being led by well-armed Iraqi Sunnis angry at being pushed from power alongside Saddam Hussein.

Although U.S. military analysts disagree over the exact size, dozens of regional cells, often led by tribal sheiks and inspired by Sunni Muslim imams, can call upon part-time fighters to boost forces to as high as 20,000 - an estimate reflected in the insurgency's continued strength after U.S. forces killed as many as 4,000 in April alone.

One hint that the number is larger is the sheer volume of suspected insurgents - 22,000 - who have cycled through U.S.-run prisons. Most have been released. And in April alone, U.S. forces killed as many as 4,000 people, the military official said, including Sunni insurgents and Shiite militiamen fighting under the banner of a radical cleric.

http://www.guardian.co.uk/worldlatest/story/0%2C1280%2C-4290373%2C00.html