BAGHDAD – 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 bombs 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.