A US military helicopter crashed northeast of Baghdad today, killing all 13 people aboard, the US military said in a statement.
It gave no details on the cause and described those aboard as military personnel, both passengers and crew, without identifying them.
The military did not identify the type of helicopter. The Blackhawk helicopter widely used in Iraq carries four crew and about 10 passengers on a typical flight.
"A US forces helicopter went down northeast of Baghdad ... Emergency Coalition Forces responded and secured the scene. Thirteen passengers and crew members were aboard the aircraft and all were killed," the US military said in a statement.
Dozens of helicopters have crashed in Iraq over the past four years since the US-led invasion, a number shot down by insurgents.
The area northeast of Baghdad has been the scene of intense fighting between US forces and guerrillas. Police in the Shia Muslim holy city of Kerbala said more than a dozen mortar rounds landed near the governor's offices as thousands gathered to begin the major, 10-day rite of Ashura.
No one appeared to have been wounded, one officer said. Police cordoned off the area, which lies about 2 km (a mile) from the main focus of the religious ceremonies.
Live television footage at the time, shortly after dark, showed the crowd undisturbed. Although police said 14 mortar rounds were fired, a source familiar with security in Kerbala, 110 km (70 miles) south of Baghdad, said the cause of the blasts in the city was unclear and may have been connected with a raid by US and Iraqi security forces on political offices.