Iraqi troops detained 15 suspects in connection with the attack, said Lieutenant Colonel Ismail Ibrahim on Saturday.
In related violence, the US military on Saturday said a bomber detonated his explosives-laden car killing five Iraqis, including three soldiers, in Falluja, west of Baghdad.
Ten others, including six soldiers, were wounded in the Friday afternoon attack. The bomber struck an Iraqi army convoy, the US military statement on Saturday said.
In nearby Habaniya, four Iraqis were killed and 15 were wounded when a car bomb exploded near a mosque on Friday.
In Mahmoudiya, about 30km south of Baghdad, police discovered the body of a Sunni tribal leader, Shaikh Arkan Shaalan Jassim al-Edwan, who had been shot to death.
Mahmoudiya police Lieutenant Adnan Abd Allah said al-Edwan was found sprawled on a damaged roadside portrait of former President Saddam Hussein.
US soldiers killed
Two US soldiers were killed and one was wounded during a smalls arms skirmish with fighters while transporting a detainee north of Baghdad, the military said Saturday.
At least 1720 US soldiers have
been killed since March 2003
A civilian and the detainee were also killed in the incident late on Friday near Buhriz, 60km north of Baghdad. Five Iraqi police were wounded, the military said.
Iraqi soldiers detained two suspects, the military said.
The names of the two dead Americans, who belonged to Task Force Liberty in north-central Iraq, were withheld pending notification of their families.
The US military also confirmed that two US soldiers were killed when their vehicle hit an improvised explosive device, also known as an IED, or roadside bomb near Ramadi in the al-Anbar governorate on Thursday.
At least 1720 members of the US military have died since the Iraq war started in March 2003.
Meanwhile in Baghdad on Saturday, a doctor in the former Iraqi army was gunned down, said an interior ministry source.
Brigadier-General Mundher al-Bayati was killed by unidentified armed men when he came out of his home in Sayidiyah in southern Baghdad after they had knocked on his door, said the source.
In the western Baghdad neighbourhood of al-Jihad, a roadside bomb that was meant to strike a passing police convoy wounded two civilians, said interior ministry and medical sources said.
On Friday, Iraqi troops and US tank and amphibious assault units launched an offensive in the western al-Anbar governorate, near the Syrian border.
US-led forces are trying to root
out fighters from al-Qaim
"Operation Spear ... began in the early morning hours with
the objectives of rooting out insurgents and foreign fighters
and disrupting insurgent support systems in and around
Karabila," US marine Captain Jeffrey Pool said in a
statement from Ramadi, capital of the al-Anbar region.
He added a total of 1000 troops were involved.
Residents in Karabila, a suburb of al-Qaim, where the suspected weapons caches were targeted, said fierce gunbattles broke out overnight and continued into the morning.
In an earlier operation, on 11 June, the US military claimed 40 fighters had been killed in the same area.
A modified US Black Hawk helicopter, known as a Pave Low, made an unscheduled landing near Qusayba, 20km west of al-Qaim, the military said.
Captain Pool emphasised that it was not shot down.