Two US soldiers were killed in separate roadside bomb explosions in south Baghdad on Thursday, the US military said in separate statements.
A third US soldier was killed, again on Thursday, when his vehicle was hit by a roadside bomb in Ramadi, 110km west of Baghdad, the US military said.
Two other military personnel were also killed, but the US military did not provide details.
Two US Marines were killed in an indirect fire attack at Saqlawiya in Falluja on Thursday, another US military statement said.
One Marine died at the scene and the second later died from his wounds at a nearby medical centre.
Two US Marines were killed in
Saqlawiya on Thursday
The names of the deceased are being withheld pending notification of next of kin and release by the US Department of Defence, the statement added.
The latest fatalities bring to 2012 the number of US military personnel killed in Iraq since the March 2003 invasion.
In related violence, an Iraqi soldier was killed and another wounded when a roadside bomb exploded near their patrol in central Falluja, 50km west of Baghdad.
Woman and child
Police officer Shamil Ali said a woman and a child were killed in subsequent gunfire.
Aljazeera also reported that two Iraqis, a man and a woman, were killed when shot by US soldiers who were storming the al-Malaab neighbourhood east of the western city of Ramadi, Iraqi medical sources said.
Iraqi Rapid Reaction Forces killed two fighters during an operation to free about two dozen people taken hostage in Khamishli, 65km south of Baghdad.
Al-Sistani backed Shia alliance
in January elections
Police said five of the hostages were found shot dead.
Eight civilians were wounded when a bomb went off near a bus station in Miqdadiya, 90km northeast of Baghdad.
Five civilians, two of them children, were injured when a mortar round landed on a residential district in Baquba, 65 km northeast of Baghdad, police said.
Meanwhile, Shia spiritual leader Ayatollah Ali al-Sistani said on Friday that he would back none of the rival blocs contesting new parliamentary elections scheduled for December, unlike in January 2005 when he endorsed the main Shia alliance.
Al-Sistani "will call on Iraqis to massively participate in the forthcoming elections but he will not back any one party", said a al-Sistani spokesman, Shaikh Abdul Mahdi Al-Karbali.
Al-Sistani rarely appears in public and usually lets aides speak for him.
"It is up to Iraqis to make their choice in accordance with their beliefs," said Karbali in a sermon at Friday prayers in the city of Karbala.