The soldiers, said to be from a so-called elite unit, under orders to track down ousted Iraqi president Saddam Hussein, carried out the raid late on Sunday.
An Iraqi policeman said all those killed, including a teenage boy, were bystanders in vehicles which US troops had shot at as they drove through the Mansur area.
A US military spokesman said he had no information on the raid except that it was carried out by Task Force 20, a special team set up to find Saddam and his key aides.
Neighbours said US troops had used explosives to burst into a villa owned by tribal chief Rabih Amin.
He returned to his home after the raid began to find soldiers had broken down the door and ransacked the house.
“I was told they had been tipped off that Saddam was hiding in my house, that he was in fact my guest,” said Amin. “But I know nothing about this.”
Amin described his ties with Hussein as “nothing special”.
Two cars outside the villa were blazing and two others were riddled with bullets.
Soldiers at the scene refused to comment and pulled out of the area quickly, suggesting that no important figures had been found.
Attacks against US soldiers are
One US soldier at the hospital where the dead and wounded were transported said: “Today has been off the wall.”
The Mansur area was also the target of four US 450 kg “bunker-buster” bombs on 7 April after occupation forces received information that Hussein and his now deceased sons were meeting in a building in the area.
Hussein’s sons Uday and Qusay were killed last week in a US onslaught on a villa in the northern Iraqi city of Mosul, after a tip-off from an informant who Washington says will claim a $30 million reward.
On Monday, grenades were lobbed at a US patrol in central Baghdad, seriously injuring two soldiers. There were strong rumours that some of the soldiers were killed but there was no official confirmation.
A Reuters journalist at the scene said they appeared to be dead but a US officer declined to confirm if they were. Nearby Iraqi policeman also said they believed some soldiers were killed.
Eyewitnesses said a man standing on a bridge dropped a grenade on their vehicle at an intersection in broad daylight.
Earlier, rocket-propelled grenades (RPGs) were fired at a tank guarding a hospital in Ba’aquba, 50 km north of Baghdad. There were no casualties.
British soldiers gather at the
Meanwhile, explosions were heard overnight in the southern Iraqi city of Basra.
Aljazeera reported the blasts were the result of British troops destroying abandoned arms caches.
But French news agency Agence France Presse said unknown assailants fired rocket-propelled grenades (RPGs) at a shop selling alcohol, wounding five people.
Neither report could be independently verified. Some hours later on Monday two US armoured vehicles came under RPG attacks in Baquba, 50km north of the capital.