Nine Iraqi police officers were killed Friday in a mortar-and-gun attack by insurgents at a checkpoint north of Baghdad, and at least a dozen people died in violence elsewhere in the country.

Police said the checkpoint assault began about 8 a.m. when two mortar rounds landed near a roadblock set up by 20 police officers in Buhriz, a small town south of Baqubah, which is about 35 miles northeast of Baghdad.

Baqubah's police chief, Gen. Ghassan Adnan Bawi, said in an interview that no one was injured by the mortar rounds but that a short time later three carloads of armed men approached the checkpoint and opened fire.

Raheem Hamad, one of 11 officers wounded in the battle, said from his hospital bed in Baqubah that the gunfight raged for almost an hour but "headquarters didn't send backup." As the police officers began running out of ammunition, he said, some fled to the safety of nearby houses. Those who remained at the checkpoint were killed, he said.

"We are powerless," Bawi said while visiting the wounded at the hospital. "We can do nothing."

Farther north, about 30 miles south of Kirkuk, five police officers were killed and five were injured when a roadside bomb exploded as a 10-vehicle convoy from the Interior Ministry's Thunder Brigade passed by, according to police Capt. Samad Mahmood. He said the convoy was protecting a group of 20 fuel trucks heading to Baghdad.

Meanwhile, an American soldier was killed Friday when a convoy in eastern Baghdad was hit by a roadside bomb, the U.S. military reported.

The military also reported that a soldier with the 1st Corps Support Command died late Thursday "as a result of non-battle-related causes" near Tallil, about 160 miles southeast of Baghdad. Since the war began, 376 U.S. service members have died in accidents or suicides, a number that represents about 19 percent of all U.S. fatalities.

Elsewhere, three people were killed by a roadside bomb in Baghdad's Dora district, and U.S. forces said they killed three gunmen near Samarra, about 65 miles north of the capital. The Associated Press reported that a young girl was killed outside Baghdad when a mortar shell apparently fired at Abu Ghraib prison missed and struck her house.

Meanwhile, the insurgent group al Qaeda in Iraq, headed by Jordanian Abu Musab Zarqawi, warned on a Web site that it would keep targeting foreign diplomats in Iraq, saying they should not back a "government of apostasy, which is appointed by the crusader occupiers." The message followed an Internet posting Thursday in which the group said it had tried two Moroccan Embassy employees kidnapped last month and sentenced the men to death.

"Despite our early and public warning to these envoys in Baghdad, and even after we targeted them, they are still here, blinded by betrayal of their religion," Friday's statement said, according to the Reuters news service. "We will spare no effort to track them down and seek our revenge, whoever they are and wherever they are, like we have done with those before them."

Shammari reported from Baqubah.