US warplanes and helicopters bombed two villages near the city of Ramadi, a hotbed of Sunni-Arab insurgents west of Baghdad, killing an estimated 70 militants, the military said Monday.
But witnesses said at least 39 were civilians.
The violence on Sunday occurred a day after Iraq voted on - and apparently passed - a landmark constitution that many Sunnis opposed.
On referendum day, a roadside bomb killed five US soldiers in a vehicle in the Al-Bu Ubaid village on the eastern outskirts of Ramadi.
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