US troops faced one of the bloodiest weeks since the occupation of Iraq as they came under rocket-propelled grenade attacks in the city of al-Hilla, 85 km south of Baghdad.
The latest killing brings the number of American soldiers killed in the past 24 hours to five.
US military officials said soldiers came under attack with small arms, RPGs and possibly an improvised explosive device near Abu Ghuraib.
The attack came hours after three American soldiers were killed in Baquba near Baghdad in a grenade attack.
The deaths of the soldiers brought to 163 the number of troops killed in Iraq since the start of the invasion, 16 more than were killed in the 1991 Gulf War.
A US military spokesman said forces were facing about 13 resistance attacks a day across the country.
US troops fired shots in the air on Sunday in the holy city of Karbala to disperse demonstrators, angry over the killing of a local man.
"We're still on the offensive here. There's still war going on in Iraq."
--US military spokesman
Our correspondent said that US soldiers shot dead an Iraqi civilian and wounded six others in the central city of Karbala, predominantly Shi'i, late on Saturday.
The killing took place near the Imam Hussein shrine, revered by Shia.
The incident occurred when American troops were providing back up to Iraqi policemen, who were trying to capture so called "armed gangs" selling contraband goods in the area.
Residents of Karbala are apparently upset that occupation troops entered the holy city.
Discontent is mounting among the Shi’i community, which Washington had regarded a staunch ally in the run-up to the war.
Shia, which make up 60 percent of Iraq’s population, had been politically un-represented and oppressed under ousted Iraqi President Saddam Hussein.
Aljazeera said the Hawza, or the top Shi’i religious and educational authority in the southern Iraqi city of Najaf, has also rejected the US-backed Iraqi Governing Council.
Iraqi papers published the pictures
of Uday and Qusay on Sunday
The 25-member council has the ability to appoint ministers and review laws but ultimate power continues to be with the US occupying administration.
In other developments, US forces detained our correspondent and cameraman in the northern Iraqi city of Mosul as they were filming the remains of a vehicle attacked by American troops.
Cameraman Nawfal al-Shahwani went on a hunger strike and was transported to hospital.
Meanwhile, the leader of the Abu al-Nasr tribes to which Hussein's family belongs said he had asked the US military to release the bodies of the ousted leader's sons, Uday and Qusay, so they could be buried according to Muslim rites.
But the leader's calls have fallen on deaf ears. Sheikh Mahmoud Nada told al-Jazeera: "The American leader said we can't right now...Meaning, let Saddam come and claim them."