The U.S. soldier serving with Task Force Baghdad was killed when a rocket-propelled grenade hit his vehicle while on patrol in the capital, the military said. The name of the soldier was withheld pending notification of next of kin.
The Defense Ministry director of operations, Brig. Gen. Abdul Aziz Mohammed-Jassim, blamed increased violence in the past two days on insurgents trying to deepen the political turmoil following the elections.
The violence came as three Iraqi opposition groups threatened another wave of protests and civil disobedience if allegations of fraud are not properly investigated.
The three blocs include the secular Iraqi National List, headed by former Shiite Prime Minister Ayad Allawi, and two Sunni Arab groups.
In other developments:
Iraq's Electoral Commission announced Monday that final results of the elections for the 275-seat parliament could be released in about a week.
Sunni Arab and secular Shiite factions have demanded that an international body review more than 1,500 complaints, warning that they may boycott the new legislature. They have also asked for new elections in some provinces, including Baghdad. The United Nations has rejected an outside review.
"We will resort to peaceful options, including protests, civil disobedience and a boycott of the political process until our demands are met," Hassan Zaidan al-Lahaibi, of the Sunni-dominated Iraqi Front for National Dialogue, said in neighboring Jordan, where representatives of the groups have met in recent days.
Among the complaints are 35 that the election commission considers serious enough to change some local results. But, said Farid Ayar, a commission official, "I don't think there is a reason to cancel the entire elections."
He also said preliminary results from ballots in early votes by expatriate Iraqis, soldiers, hospital patients and prisoners showed a coalition of Kurdish parties and the main Shiite religious bloc each taking about a third. Those nearly 500,000 votes were not expected to alter overall results significantly.
Preliminary results from the election have shown the United Iraqi Alliance, the religious Shiite coalition dominating the current government, with a large lead. But it is unlikely to reach the two-thirds majority needed to avoid a coalition.
Bahaa al-Araji, a member of the Shiite alliance, said the group was preparing to negotiate with other political blocs and had already met with the Sunni Arab Iraqi Islamic Party.
Al-Araji also said likely candidates for prime minister were current Prime Minister Ibrahim al-Jaafari, who heads the Islamic Dawa party, and Adel Abdul-Mahdi, who belongs to the other main Shiite party, the Supreme Council of the Islamic Revolution in Iraq.
Every time there has been a defining event in Iraq since the fall of Saddam Hussein in 2003, there has been a period of calm. They included the June 28, 2004, transfer of power from the U.S.-led Coalition Provisional Authority, the Jan. 30 elections, and the Oct. 15 constitution referendum.
The recent lull in violence ended Sunday, with the deaths of 18 people.
On Monday, a suicide car bomber slammed into a police patrol in the capital, CBS News' Pete Gow reports, leaving three dead, officials said, and a suicide motorcycle bomber rammed into a Shiite funeral ceremony, killing at least two and wounding 26, said Maj. Falah Mohamadawi of the Interior Ministry.
A mortar then killed two people in a predominantly Shiite neighborhood.
Four other car bombs killed at least two people and gunmen killed five officers at a police checkpoint 30 miles north of Baghdad, officials said.
In other violence, gunmen raided a house in southern Baghdad, killing three people, police Capt. Qassim Hussein said. Gunmen attacked the house again when police arrived to remove the bodies, wounding two officers, police said.
Also, a Shiite cleric in the southern city of Najaf and a man in the northern city of Mosul were gunned down. In Baghdad, a civilian driving his children to school and a professor were killed.
A car bomb also targeted the governor of Diyala province, killing a body guard, while gunmen killed a member of Diyala city council.