Four U.S. soldiers were killed and six were wounded late Tuesday when insurgents attacked an Army patrol near the northern town of Baiji, the military announced Wednesday.

Separately, the military announced that a soldier fighting with a Marine unit was killed Tuesday by small arms fire in combat operations near Habbaniyah, 50 miles west of Baghdad.

The killings brought to ten the number of U.S. service members whose deaths have been announced since Saturday while 38 have been killed in the month of August.

Regarding the Baiji attack, the military said a roadside bomb detonated as the patrol was investigating reports of earlier explosions in the area. The patrol then received small arms fire.

Mohammed Attallah, a farmer, said "we heard sounds of explosion at about 11 p.m. followed by heavy shooting."

Police in the town told wire services that two Humvee patrol vehicles and a larger armored vehicle appeared to have been wrecked and burnt out. They were surrounded by U.S. troops after the incident.

Also Tuesday, a suicide car bomber attacked a convoy of U.S. Army Humvees across the Tigris River from Baghdad's fortified Green Zone, killing one soldier and wounding two others. At least 12 Iraqis were killed in the afternoon blast, and the dead and wounded were stacked on wooden pushcarts to be taken to a nearby hospital.

On Monday, a Marine was killed by small arms fire in Ramadi in western Iraq, where U.S. forces have suffered heavy casualties in recent days, the military said in a statement.

A U.S. general said Tuesday that the violence would likely escalate as the deadline approached for drafting a constitution for Iraq.

"If you look at the past few months, insurgents have not been able to sustain attacks, but they tend to surge every four weeks or so. We are right in the middle of one of those periods and predicted this would come," said Army Brig. Gen. Karl Horst, the deputy commander of the 3rd Infantry Division, which oversees Baghdad. "If they are going to influence the constitution process, they have only a few days left to do it, and we fully expect the attacks to continue."

In other violence Wednesday, Reuters reported that a suicide bomber killed six people and wounded 14 when he drove a car at a police patrol in the Ghazaliya district of western Baghdad. Two of the dead and two of the wounded were policemen and the remaining casualties were civilians.

On Tuesday, rebels shot dead 10 policemen in five attacks across the capital.

The military also announced Wednesday the death of a service member in Afghanistan as the result of a roadside bomb attack Tuesday near Ghazni. His unit was "conducting operations designed to disrupt enemy activity in the region at the time of the attack," the military statement said.

Bassam Sebti reported from Baghdad. Fred Barbash reported from Washington.