A U.S. soldier has been killed in an ambush near the southern Iraqi town of Najaf (search), and there are reports that another GI may have been assassinated while buying video compact disks in Baghdad (search).

The confirmed death occurred Thursday night when a GI was investigating a car theft in Najaf, 100 miles southwest of Baghdad, a statement from U.S. Central Command (search) said.

The soldier, who was attached to the 1st U.S. Marine Expeditionary Force (search), died before a medical evacuation team arrived, Centcom said.

The soldier's name was being withheld pending notification of relatives. No other details were immediately available.

In the second incident, a U.S. soldier was said to have been shot in the head Friday while buying video compact disks in Baghdad.

According to Reuters, a video store owner and other witnesses said the soldier had come into the shop late in the morning and picked up two DVDs.

"He took out dollars from his pocket and as I looked at the money I heard a bang. He froze and then fell backwards," the owner told Reuters Television. Witnesses said they saw a young man shooting the soldier point-blank in the head.

The Associated Press reported that witnesses said the shooting occurred on a sidewalk. Ammar Saad, a 44-year-old vendor, told AP the soldier was shot in the neck at close range and appeared to have been killed.

Saad and another witness, 20-year-old porter Jassem Obeid, said the assailant escaped into crowds at a nearby market.

U.S. military spokesmen in Baghdad said they had heard of the incident but were unable to confirm it.

Meanwhile, authorities interrogated six suspects detained in connection with the disappearance of two American soldiers, said Sgt. Patrick Compton, a U.S. military spokesman in Baghdad.

U.S. forces kept up ground and aerial searches that have so far failed to find the soldiers or their Humvee, Compton said.

The pair were guarding the perimeter of a rocket demolition site near the town of Balad, 25 miles north of Baghdad, when they failed to answer a radio call and were reported missing Wednesday night, Compton said.

"We don't know if they were abducted or they were just killed," Compton said.

Just northwest of Baghdad Friday morning, a U.S. Army truck struck an explosive device on a dirt road. A U.S. soldier and an eyewitness said wounded Americans were evacuated by helicopter.

The soldier, who spoke on condition of anonymity, said the Americans were driving to Baghdad to make telephone calls to their families when the explosion happened.

Ambushes and hostile fire elsewhere in Iraq on Thursday killed at least one U.S. soldier, two Iraqi civilians and wounded at least eight other Americans, as armed resistance to American and British military occupation appeared to be rising.

Until recently, almost all violence against U.S.-led occupying forces in Iraq had centered around the Sunni Muslim-dominated area north and west of Baghdad, where former Iraqi leader Saddam Hussein enjoyed a degree of support. In the past few days, attacks have spread to the Shiite-dominated south.

Late Thursday, a British plane dropped leaflets on the southern town of Majar al-Kabir, where six British soldiers and at least five Iraqi civilians were killed in violent clashes on Tuesday.

The leaflets stated that the U.S.-led coalition forces regret the loss of life among Iraqi civilians, and added that coalition forces were not behind the incident.

"We will not return to punish anyone since these are the methods of Saddam's regime. We will return to set up good relations with you because of our concern about a secure Iraq," the three-paragraph statement read. "Don't let rumors ruin our good relations."

The leaflet added that British forces -- who have not been seen in the volatile town since Tuesday's clash -- would return to Majar al-Kabir to repair the damage done during Saddam's rule, without saying when.

The Associated Press contributed to this report.