Communist rebels claimed responsibility Saturday for killing a U.S. Army colonel who advised this country's military, and officials fearing more attacks bolstered security for U.S. forces.

Philippine troops near the six U.S. military installations in the country were reinforced and put on maximum alert immediately after Col. James "Nick" Rowe was slain Friday, according to Gen. Renato de Villa, the Philippine army's chief of staff. Rowe's Filipino driver was wounded.Communist assassins in a stolen car sprayed Rowe's vehicle with bullets while he was on his way to work in suburban Quezon City. The killers escaped.

The 51-year-old Rowe, who was a prisoner of war in Vietnam, served as chief of the ground forces division of the Joint U.S.-Military Advisory Group, which provides training and logistical support to the Philippine military.

Rowe, a native of McAllen, Texas, was a decorated Vietnam War veteran who was held in a cage for five years by the Viet Cong until he escaped in 1968. He wrote a book about the ordeal titled, "Five Years to Freedom."

The communist New People's Army General Command claimed responsibility for his assassination in a statement delivered Saturday to news agencies.

The statement threatened further attacks if the United States continues to back President Corazon Aquino's fight against the 20-year communist insurgency.

"The death of Col. Rowe signifies the firm commitment of the revolutionary forces to continue military actions against U.S. personnel and installations, as these are manifestations of the arrogant trampling of U.S. imperialists on the Filipino people's independence and sovereignty," the statement said.

The U.S. Navy ordered additional security for the 1,000 sailors on the flagship USS Blue Ridge of the 7th Fleet. The ship arrived Friday for a four-day Manila port call.

Lt. Mike Andrews, the fleet's spokesman, said the sailors were told to travel in groups and avoid dark alleys.

Filipino soldiers used bomb-sniffing dogs Saturday to check luggage at Manila airport, fearing terrorists might try to plant bombs on departing planes.

U.S. Ambassador Nicholas Platt called the killing a "cowardly" act, and presidential spokesman Marlin Fitzwater said U.S. authorities would help the government search for the killers.

No date had been set for memorial services or for flying Rowe's body back to the United States.

His killing came five days after the rebels announced they were "determined to make U.S. imperialism pay dearly for the continuing stay of its bases and its escalating intervention in our people's affairs."