Antonella Notari, of the ICRC, said civilians must be spared as much as possible, though added that military authorities have the right to try to ensure the safety of their staff and to stop and search vehicles.

"We hope that they took all the necessary measures to warn the people, to clearly alert them," she told reporters.

US troops shot dead seven women and children at a checkpoint near the central Iraqi city of Najaf, 150 kilometres (95 miles) south of Baghdad, on Monday afternoon, US officials said on Tuesday.

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.

A US field commander told AFP that, with US soldiers on edge after a suicide car bomb attack on Saturday that killed four comrades, the unit that opened fire on the minibus had respected their rules of engagement.

"Checkpoints have, of course, the right to try and defend their own security and the security of their personnel so they may search vans, they may stop vehicles, there are certain rules on how you proceed in that," Notari said.

"I can't comment on what exactly happened on the spot, I can only deeply regret that again they were civilians who were hit," she added.

ICRC would not comment on incidents in the field, she insisted to reporters.

"We are not witnesses to all of this, we cannot be the arbitrator on who is doing what in the field when we are not even present," she added.

The Geneva-based organisation has 14 international staff in the cities of Baghdad, Basra and Arbil, plus local staff in other northern parts of Iraq.

SPACE.WIRE