Three other U.S. soldiers, an Iraqi interpreter and nine Iraqi civilians were injured in the explosion, which inflicted the most casualties on U.S. forces in Baghdad since the surge began last year, The New York Times reported.

Meanwhile, a car carrying explosives was detonated outside a hotel in Sulaimaniya in northern Iraq, killing two people and wounding 30 more, the Times reported. It was the worst attack in the Kurdish city in several years, the newspaper said.

Elsewhere, a pro-government tribal sheik died Monday in one of two suicide bombings in Diyala Province, police said. Sheik Thaer al-Karkhi died in the blast that killed three other people, including his 5-year-old niece, KUNA reported. An 18-year-old woman set off a bomb in front of the sheik's home, the Kuwaiti news agency said.

Karkhi lead an Awakenings Council group, a largely Sunni local security group that fights insurgents.

Police said another suicide bomber neared several Iraqi security forces and set off his bomb, killing two civilians and wounding 20 people, CNN reported.