A car bomb exploded Tuesday in a mostly Shiite area of eastern Baghdad, killing at least 10 and wounding 28, police said. Another blast killed a woman and two of her young sons in the capital, officials added.

The latest violence came after the U.S. military reported the deadliest day in almost three months for American service members in the Iraq war. Ten U.S. troops died, including five Marines killed in a vehicle accident in western Iraq. Two Marines and a sailor were still missing after the truck overturned near Asad air base.

The car bomb went off in the poor, mostly Shiite area of Habibiyah, and damaged several cars and nearby sandwich stands, police said. Chaos ensued, and militants from radical cleric Muqtada al-Sadr's Mahdi Army fired in the air to clear the crowds.

The bombing in the mostly Shiite neighborhood of New Baghdad hit shortly after 7 a.m., killing the woman and two boys, 9 and 12. A third son, aged 13, was wounded, as were two brothers of a different family living in the same home, police said.

North of the capital, a car bomb targeted a convoy carrying a Samarra city council member's son, killing a security guard and a driver and wounding three other guards. The son, 19, was not harmed.

In southern Iraq, gunmen killed a policeman and wounded another as the two were driving in the city of Basra, police said.

Police discovered four corpses, apparent victims of the sectarian violence gripping Iraq. Two were found near a highway in western Baghdad's mostly Sunni neighborhood of Khadra, both handcuffed and showing signs of torture, and another in southwestern Baghdad's Shurta district, shot in the head. The other, also handcuffed, was found floating in a small river south of the capital, police said.

The continuing violence made talks to form a new government even more urgent. Politicians have been at a stalemate for months, primarily due to disagreement over who the next prime minister should be.

Sunni and Kurdish politicians have called for the Shiite bloc to replace Ibrahim al-Jaafari, the current prime minister, as its nominee. Last weekend, two prominent Shiite politicians also joined calls for him to step aside.

The only faction showing steadfast loyalty to al-Jaafari appeared to be the one led by al-Sadr, the radical Shiite cleric. Some 2,500 people marched in support of al-Jaafari in Sadr City, calling for Iraqi leaders to speed up the formation of the government and carrying banners reading "Down with the Conspiracy." The demonstrators also bore an empty black coffin, with the words "Constitution" and "Political Process."

Adnan al-Dulaimi, a Sunni Arab politician, said Tuesday that Sunnis were still insisting on a different nominee and hoped to hear back from the main Shiite bloc in a few days.

A prominent Shiite politician among the two publicly calling for al-Jaafari to step aside continued to express his faltering support.

"In my belief, there is no way left (for al-Jaafari), considering that other parliamentary blocs are still closing doors ... and the constitutional choices in Dr. al-Jaafari's hands do not enable him to win the legal quorum in order to receive a new mandate as prime minister," Shiite legislator Jalal Eddin al-Sagheer told Lebanese television Tuesday.

Rising tensions between Shiite and Sunni Muslims have led to a marked increase in Iraqi civilian deaths. At least 1,038 civilians died last month in war-related violence, according to an Associated Press count.

The AP count showed at least 375 Iraqi civilians killed in December, 608 in January and 741 in February. Most of the increase appeared to be a result of a sharp rise in the number of civilians found dead throughout Baghdad — the apparent victims of sectarian reprisal killings.

U.S. casualties had appeared to be on the decline, with last month the least deadly for American troops since February 2004. But 14 troops have already died in the first three days of April — nearly half the number who died in all of March.

In addition to the five Marines killed in the vehicle accident, three Marines and a sailor were killed by "hostile fire" in the same province, the military said. No further details, including the precise location, were released.

Army Pfc. Jeremy W. Ehle of Richmond, Va., was killed when his patrol came under fire near Hit, 85 miles west of Baghdad. Ehle, who arrived in Iraq last month, was part of the Army's 1st Battalion, 36th Infantry Regiment, 1st Brigade, 1st Armored Division stationed in Friedberg, Germany.

That many American troops had not died in a single day since Jan. 7, when 18 troops were killed, according to the Web site icasualties.org.

As of Monday, 2,344 members of the U.S. military have died since the beginning of the Iraq war in March 2003, according to an AP count.

Elsewhere, police said three Iraqi army officers were arrested in connection with an attack on an oil pipeline in Hawija, 150 miles north of Baghdad, last week.

The Iraqi government also announced the arrest in Anbar province of five "terrorists," including two Sudanese who entered through Jordan.