The cause of the crash of the OH-58 Kiowa helicopter that killed its two-man crew near Haditha, 120 miles from the capital, was not determined, said Brig. Gen. Mark Kimmitt. A witness, Emad Rasheed, 45, said he saw a missile hit one of two choppers in the area.

With the latest crash, the US military has lost 15 helicopters since the occupation began in May -- most to hostile fire. At least 60 Americans have been killed in the crashes.

In Baghdad, attackers fired a rocket-propelled grenade at a major Shia Muslim shrine overnight, officials at the shrine said. The RPG punched a hole in an outer wall of the Kazimiyah shrine in a northern neighborhood of the capital but caused no injuries.

The attack on the shrine came on the fourth day of the Islamic month of Muharram, a sacred period when thousands of Iraqi Shiites and Iranian pilgrims have converged on Kazimiyah, where two Shiite saints are buried, and other Shiite shrines in cities of southern Iraq.