Four US soldiers were abducted during a sophisticated sneak attack last week in the Shiite holy city of Karbala, the US military confirmed on Friday.
It said three were shot to death and a fourth was mortally wounded by a gunshot to the head in a neighboring province, far from the compound where they were captured.
Two of the four were handcuffed together in the back seat of a truck near the southern Iraqi town of Mahawil.
On Jan. 20, the day of the raid on a security meeting in Karbala, the military said five soldiers were killed repelling the attack.
The brazen assault, 80km south of Baghdad, was conducted by nine to 12 militants posing as a US security team, two senior US military officials as well as Iraqi officials said.
They traveled in black GMC Suburban vehicles, had US weapons, wore new US military combat fatigues and spoke English, Iraqi and US military officials said.
The confirmation emerged after nearly a week of inquiries.
"Two soldiers were found handcuffed together in the back of one of the SUVs. Both had suffered gunshot wounds and were dead. A third soldier was found shot and dead on the ground. Nearby, the fourth soldier was still alive, despite a gunshot wound to the head," the military's report said.
"The precision of the attack, the equipment used and the possible use of explosives to destroy the military vehicles in the compound suggests that the attack was well rehearsed prior to execution," said Lieutenant Colonel Scott Bleich-wehl, spokesman for the Multinational Division-Baghdad.
"The attackers went straight to where Americans were located in the provincial government facility, bypassing the Iraqi police in the compound," Bleichwehl said. "We are looking at all the evidence to determine who or what was responsible for the breakdown in security at the compound and the perpetration of the assault."
The Karbala raid began after nightfall at about 6pm on Jan. 20, while US military officers were meeting with their Iraqi counterparts on the main floor of the Provisional Joint Coordination Center in Karbala, US and Iraqi officials said.
Iraqi officials said the approaching convoy of black GMC Suburbans was waved through an Iraqi checkpoint at the edge of Karbala.
A top Iraqi security official for Karbala Province said that the Iraqi guards at the checkpoint radioed ahead to the compound to alert their compatriots that the convoy was on its way.
Iraqi officials said the attackers' convoy divided upon arrival, with some vehicles parking at the back of the main building where the meeting was taking place, others parked in front.
The attackers threw a grenade and opened fire with automatic rifles as they grabbed two soldiers inside the compound. Then the guerrilla assault team jumped on top of an armored US Humvee and captured two more soldiers, US military officials said.
One US soldier was killed in the melee at the compound, and three were wounded.
The attackers captured the four soldiers and fled with them and the computer east toward Mahawil, US military officials said.
The Iraqi officials said the four were captured alive and shot just before the vehicles were abandoned.