Iraqis examine a crater after a roadside bomb struck a British patrol Thursday in Basra, Iraq. The patrol struck a roadside bomb and was hit by small-arms fire, British military spokeswoman Capt. Katie Brown said.

Baghdad, Iraq ? The U.S. military reported Thursday that eight U.S. soldiers were killed in the Baghdad area over the past three days as militants fought back against a security plan in its eighth week. An Army helicopter went down south of the capital, wounding four, after an Iraqi official said insurgents fired on it.

Four British soldiers – including two women – died Thursday in an ambush that Prime Minister Tony Blair called an “act of terrorism,” suggesting it may have been carried out by elements linked to Iran but stopping short of blaming Tehran.

One U.S. soldier died and two were wounded in a roadside bombing Thursday in restive Diyala province north of Baghdad, the military said. Four others died Wednesday in two roadside bomb explosions in southern Baghdad and north of the capital, while another was killed by small-arms fire in the eastern part of the city. Two other soldiers were killed by small-arms fire on Tuesday – one in eastern Baghdad and another on foot patrol in the southern outskirts of the capital.

The U.S. military said the downing of the helicopter carrying nine people was under investigation.

An Iraqi army official, speaking on condition of anonymity because of security concerns, said the helicopter went down after it came under fire from anti-aircraft guns near the Sunni insurgent stronghold of Latifiyah, 20 miles south of Baghdad. The U.S. military did not confirm that account.

It was the ninth U.S. helicopter to go down in Iraq this year. The U.S. military has studied new evasive techniques, fearing insurgents have acquired more sophisticated weapons or have figured out how to use their arms in new and effective ways.

The deadly attack against the British patrol in southern Iraq was the greatest loss of life for Britain in more than four months and it cast a shadow over celebrations marking the return of 15 British sailors seized by Iran two weeks ago in disputed waters in the Persian Gulf.

“Just as we rejoice at the return of our 15 service personnel so today we are also grieving and mourning for the loss of our soldiers in Basra, who were killed as the result of a terrorist act,” Blair said.

The British patrol struck a roadside bomb and was hit by small-arms fire early Thursday in the southern city of Basra, British military spokeswoman Capt. Katie Brown said. The explosion created a 9-foot crater in the road. Hours after the attack, a British soldier’s helmet was still laying in the street among dozens of spent bullets.

A civilian interpreter was also killed and a fifth British soldier in the unit was seriously wounded, Brown said.

Blair raised the possibility that Iranian-linked fighters may have sprung the ambush, although he conceded it was too early to directly accuse Tehran.

“Now it is far too early to say that the particular terrorist act that killed our forces was an act committed by terrorists that were backed by any elements of the Iranian regime, so I make no allegation in respect of that particular incident,” Blair said.

He added, however, “This is maybe the right moment to reflect on our relationship with Iran.”

The U.S. military has accused Iran of providing sophisticated roadside bombs known as explosively formed projectiles, or EFPs, to Shiite militias. British Lt. Col. Kevin Stratford-Wright said all of those killed were in the vehicle that was struck by the roadside bomb, although he declined to say whether it was an EFP, saying only that “it was certainly a powerful device.”