ITH V CORPS HEADQUARTERS, near the Kuwait border, March 29 — The bodies of four American servicemen have been found by the Marines in a shallow grave in the battle-worn city of Nasiriya, near the Euphrates River.

Military officials said they believed that the four were executed by Iraqi paramilitary forces after they were seized in an ambush last Sunday.

Military officials declined to speculate about whether the four bodies were those of captured American soldiers who were shown alive by Al Jazeera network last weekend. The military had heard reports that the soldiers were executed after appearing on the Arab network, but there had been no confirmation.

On Friday, a Marine unit found the four bodies in a freshly dug grave near a house in the northeast corner of Nasiriya. An Army official said the bodies were wearing American military uniforms. But confusion remained concerning their branch of the military.

Today a forensic team, military investigators and a member of the V Corps Staff Judge Advocate's office was being flown to the site. Officers said the deaths were tentatively being treated as a war crime.

The soldiers seized at Nasiriya were among 10 listed as missing in action since the fighting began. V Corps officers said the names of the soldiers found dead would be released after their families were notified.

The ambush took place in Nasiriya, in southeastern Iraq, an important crossing point over the Euphrates northwest of Basra.

According to Army officers, soldiers of a maintenance unit were traveling on Highway 1, a main north-south artery, in darkness in a convoy of six vehicles around 1 a.m. last Sunday near Nasiriya.

The unit had been sent to supply an antiaircraft battery in the area.

At a certain point the convoy took a wrong turn, mistakenly leaving Highway 1. As the convoy moved toward the first of several bridges into the town, the Americans realized they had taken a wrong turn, officials said.

As the Americans made a hasty U-turn, they were confronted by two Iraqi T-55 tanks. A company-size Iraqi military unit was also moving toward the Americans. The American soldiers came under rocket and small-arms fire.

In the fight that followed, the first two vehicles — a Humvee and a tool truck — were separated from the four other vehicles.

An Army captain in the Humvee drove the vehicle carrying wounded soldiers through the gunfire. According to one account, the officer drove nearly four miles before being forced to stop when the bullet-riddled tires finally went flat.

The officer got out and began changing the tires of the Humvee, when a United States Marine unit on patrol saw him and the soldiers in his vehicle, officers said. The marines immediately called in a medevac helicopter, which evacuated the officer and his wounded soldiers. Some of the soldiers were seriously hurt; one was shot in the jaw.

The marines resumed their patrol, looking for fedayeen, the Iraqi paramilitary force. Within minutes, they came upon two American vehicles, smashed with bullets. Two other vehicles were burning. No Americans were in sight.

Hours later, pictures of American soldiers, some dead and some captured, were shown on the Arab television station Al Jazeera. Some soldiers appeared to have bullet wounds to the head. The uniforms of other soldiers were stained with blood.

One captured soldier was asked, with Iraqi television microphones in front of him, why he had come to fight the Iraqi people.

"I didn't come here to kill anyone," the soldier said. "I was told to shoot only if shot at."

One soldier said, "I follow orders." Asked if the Iraqi people had greeted him with flowers or guns, the soldier replied, "I don't understand."

Within 24 hours, the Army was hearing reports that some of the soldiers had been executed after appearing on television.