Two US soldiers were missing on Sunday after their rescue helicopter crashed into northern Iraq's Tigris river following a patrol boat accident that left another US servicemen missing and killed two Iraqi policemen and a civilian.
The OH-58 Kiowa Warrior helicopter splashed down in the river near Mosul during a mission to find another US soldier lost in the waters when a patrol boat capsized, the US military said.
"A search for the two pilots is underway," an American spokesman said, adding that the US soldier from the patrol boat was also still missing.
"The helicopter was on a search and rescue mission for a US soldier reported missing when the boat he was in capsized at approximately 5:15 pm (1415 GMT) today," he said.
The spokesman said the boat contained three other US soldiers and members of the Iraqi police force patrolling the waters around Mosul.
"The other soldiers are reported safe, two Iraqi police and one Iraqi translator are reported dead. An investigation is underway," he said.
A senior police official in Mosul said the 101st Airborne Division helicopter had crashed after flying at low altitude into cables strung across the river.
The cables are used by Iraqi paramilitary civil defence soldiers for pulling un-powered vessels across the broad river, which runs from Turkey through Syria, before traversing Iraq to the Persian Gulf.
The US military said Iraqi police and fire-fighters were assisting with the search for the survivors.
More helicopters and military aircraft were circulating over the accident site following the crash, the police spokesman said.
Sunday's crash was the fifth US helicopter crash in Iraq this year, most caused by hostile fire.
Meanwhile, three perished when a car packed with explosives rammed a checkpoint west of Fallujah and another were killed just hours earlier by an improvised bomb north of the town.
Another soldier died from wounds received in a rocket propelled grenade attack on his Bradley fighting vehicle in the northern town of Baiji.