BAGHDAD - A US helicopter went down after coming under fire Thursday in a Sunni militant stronghold south of Baghdad but there was no immediate word on casualties, an Iraqi army official said. The US military said it was looking into the report.

An Iraqi soldier stands guard at a checkpoint in central Baghdad, Iraq, Wednesday, April 4, 2007. [AP]

Gunmen opened fire on a Black Hawk helicopter at about 7:30 a.m. as it flew over Latifiyah, 20 miles south of Baghdad, the official said, speaking on condition of anonymity because he was not authorized to release the information.

The helicopter went down in a rural area and US forces had cordoned off the site, the official said. He had no information on casualties but said the militants apparently were using anti-aircraft heavy machine gun.

Latifiyah is part of the area dubbed the Triangle of Death because of frequent insurgent attacks.

The last helicopter incident in Iraq occurred on March 1, when an OH-58 Kiowa helicopter made a "hard landing" in northern Iraq leaving the two crew members wounded. A week earlier, ground fire forced the downing of a Black Hawk north of Baghdad.

With Thursday's incident, at least nine US helicopters have crashed or been brought down by hostile fire this year in Iraq.