WASHINGTON - U.S. Army officials are investigating allegations that American soldiers killed several detainees after they were captured on a battlefield in southwest Baghdad last year, officials said Tuesday.

Military officials said the incident under review took place about six months ago in the Rasheed district and involved soldiers with the 2nd Brigade of the 1st Infantry Division. The brigade, which is based in Germany, was deployed to Iraq from September 2006 to November 2007.

The detainees allegedly were killed at the point of capture and never taken to a U.S. or Iraqi base for questioning, said Paul Boyce, a U.S. Army spokesman. The military did not reveal how many soldiers may have been involved, how many detainees may have died or who made the allegations. Frequently, such allegations surface months after an incident, when soldiers come forward or talk among themselves.

Soldiers from at least one company of the 2nd Brigade were questioned by investigators last week in Germany. The inquiry is being led by the Army’s Criminal Investigation Command.

In Iraq on Tuesday, it was another day of high-profile violence in the northern city of Mosul, where a suicide bomber detonated his car near an American military convoy. One Iraqi was killed and 15 others were injured, Iraqi police and U.S. military officials said.

Mosul is considered the last urban stronghold for the militant group Al Qaeda in Iraq. The attack came one day after five U.S. soldiers were killed by a roadside bomb and less than a week after a booby-trapped apartment building exploded, killing as many as 60 people.

To the south in Muqdadiya, security officials said they found nine corpses and 10 severed heads in the countryside. The nine corpses, all male, were found blindfolded, handcuffed and shot in the head. The 10 heads also were found blindfolded, Diyala provincial police officials said.

But another Diyala police official gave a different version of the findings, saying that eight heads and eight corpses had been discovered over the course of several months. The bodies were being moved from Muqdadiya to Baqubah, the official said, because of a broken freezer at the morgue.

U.S. military officials have long struggled to gain control of Diyala, a largely rural stronghold of Al Qaeda in Iraq. American troops helped take back the provincial capital of Baqubah last year, only to drive insurgents into outlying communities such as Muqdadiya. This month, thousands of troops descended on the Diyala River valley in another effort to strike at the group, which military officials say is foreign-led but whose foot soldiers are primarily Iraqis.

In Tharthar, north of Fallouja in Anbar province, Iraqi police reported clashes between a group of gunmen and members of the nearby Saqlawiya Awakening Council. Police said 20 gunmen were killed in the battle; a member of the U.S.-backed security force of local citizens said 22 people had died.

“We were trying to capture a group of terrorists who had a stronghold there and were robbing and killing citizens driving along that road,” said Alahi Ahmed, a member of the Awakening Council. “Our aim was to secure the pathway and cleanse it from these thieves.”

Barnes reported from Washington and Yoshino from Baghdad. Special correspondents in Mosul, Ramadi and Baghdad contributed to this report.

© 2008 The Los Angeles Times