Suspected communist guerrillas armed with assault rifles shot and killed an American Vietnam War hero Friday in his car two blocks from his office at U.S. military headquarters in the capital, authorities said.

Col. James (Nick) Rowe, 51, ground forces director of the Joint U.S. Military Advisory Group, was hit by a single bullet in the back of the head and died at the Philippine armed forces medical center about an hour later, police said.Rowe's driver, Joaquin Benoya, was wounded but was able to drive two blocks to the heavily guarded cream and brown JUSMAG offices in suburban Quezon City.

U.S. Ambassador Nicholas Platt said the United States "lost a genuine hero" in Rowe, of McAllen, Texas, who spent five years as a prisoner of war in Vietnam until he escaped. He was decorated for his service in Vietnam and later wrote a book about his ordeal titled "Five Years to Freedom."

Platt said Rowe was "on duty in support of an ally fighting to protect its democratic institutions" when he was killed. "We will not be deterred by terrorists. Nick would have it no other way," Platt said.

President Corazon Aquino told reporters the Philippine military was conducting an investigation and was extending all the necessary assistance to U.S. officials.

Asked if her government could guarantee the safety of the Americans, Aquino said, "Well, I think they had received warnings before and I guess they had taken the necessary measures, but apparently that was not adequate enough."

Col. Victor Tiangco, police northern sector commander, said Rowe's Mitsubishi car was turning toward JUSMAG when it was cut off by a maroon car and gunmen, some wearing hoods, opened fire with M-16 rifles.

"Twenty-one bullets hit the car. Unfortunately, one hit Rowe," Tiangco said.

Officials said Rowe's car was partially armored and said the bullet that hit Rowe apparently entered through an unprotected part of the vehicle.

Police said the gunmen's car was found abandoned in a working class district about four miles from the scene of the shooting. M-16 shells were found inside the vehicle.

There were no claims of responsibility for the 7:15 a.m. attack on Rowe, but Philippine military officials quickly blamed the communist New People's Army, which has been battling the government for 20 years.

It was the first attack on American military personnel in 18 months.