"We're very concerned about it and very sorry that it happened," Major General Buford Blount, commander of the Third Infantry Division, said.

But he stressed that, with US soldiers on edge after a suicide car bomb attack Saturday that killed four comrades, the unit that opened fire on the minibus had respected their rules of engagement.

His words echoed an official statement issued by US Central Command, which in part read: "In light of recent terrorist attacks by the Iraqi regime, the soldiers exercised considerable restraint to avoid the unnecessary loss of life."

The shooting occurred Monday at a checkpoint near Najaf, 150 kilometersmiles) south of Baghdad.

The seven victims were in a vehicle peppered with shots by soldiers from Blount's division.

US military officials in Qatar said the vehicle had not stopped at the checkpoint despite the US troops reportedly firing warning shots. Two other people in the vehicle were wounded, while four escaped unharmed.

Blount was at a loss to say why the vehicle did not heed instructions to stop before the checkpoint, and speculated that maybe they "were trying to escape from Karbala and thought this was a regime checkpoint."

He said he had heard that Iraqi death squads had taken over homes in Karbala, which lies north of Najaf, and were forcing families living near a hospital to leave.

He also said that his forces had in one encounter seen Iraqi fighters herding women and children ahead of them as human shields.

In that incident, one woman who broke away was shot in the back by the Iraqis and US troops put up a smokescreen to rescue her and fly her out for medical treatment.

The general added that his men had experienced "lots of contact" in the region and believed that Iraqi militias loyal to Iraqi Saddam Hussein were moving their fighters around using buses.

Because of that hostile situation, the soldiers who killed the civilians Monday had merely been enforcing security measures, he said.

"The bus committed a hostile act. It may have been unintentional," he said.

Orders were now going out to try to limit repeats of such incidents, particularly by way of putting up more barriers before the checkpoints to force drivers to a complete halt well before the troop positions, he said.

Civilians would also be encouraged to stay at home and not move around, he said.

SPACE.WIRE