MANILA, OCT. 26 -- New accusations that U.S. government personnel were involved in the abortive Aug. 28 coup showed signs today of escalating into a major diplomatic issue for President Corazon Aquino, at the same time highlighting sensitivity here to any hint of meddling by the Philippines' former colonial power.

The accusations began with a newspaper report last week that at the height of the August coup attempt, Lt. Col. Victor Raphael, an assistant military attache at the embassy, was inside Camp Aguinaldo, the armed forces headquarters that was in the hands of rebel troops. The report, in the leftist newspaper Malaya, also said Raphael at one point tried to dissuade the commander of a progovernment assault force from attacking Honasan's position.

Raphael is known to be a close personal friend of Col. Gregorio (Gringo) Honasan, leader of the aborted coup, and a frequent golfing partner of many of the reformist middle-level officers who led the failed revolt.

Last Thursday, Nicholas Platt, the new ambassador here, confirmed in a lunch with foreign correspondents that Raphael had been inside Camp Aguinaldo but said the attache's job was to keep track of the fast-moving developments. "He was doing his job," Platt said, adding that Raphael was a "trusted member" of the embassy staff.

Today, Manila newspapers reported -- and the embassy confirmed -- that another attache, Maj. Dennis Fawler, who was inside Villamor Air Base came under fire from both government and rebel troops, and that his embassy-supplied bulletproof car was hit repeatedly with bullets. Villamor was also in the hands of rebel troops during the coup attempt.

Gen. Fidel Ramos, the armed forces chief-of-staff, said on Saturday that he had investigated Raphael's actions during the coup and sent a report to Manila's Department of Defense. "We leave it to the civilian authorities to act on the matter," Ramos told a news conference.

Some military sources here said they suspect the new charges are being generated by Ramos' faction within the armed forces general headquarters. These officers are described as suspicious of the attaches' close ties to the Honasan group, and also angered by the widespread perception here that U.S. officers are critical of Ramos' ability to defeat the communist insurgency.

"It's all a concoction coming from Ramos' people," said one officer with close links to Honasan. "You could say any attache who talks to any soldier is guilty of interference."

Today, however, the issue showed signs of escalating. The acting house speaker, Rep. Antonio Cuenco, told a breakfast meeting that "one committee has been instructed to go deep into this thing, and ferret out the truth regarding American intervention." Sen. Teofisto Guingona added that the Senate would likely launch its own probe.

Guingona also said that Aquino had instructed the secretary of foreign affairs to investigate the incident, but neither the presidential palace nor the foreign affairs department would confirm it. Aquino had apparently been trying to play down the issue to avoid a major diplomatic row, but the congressional probes -- fueled by intense media coverage -- now seemed likely to keep the matter alive.

{Undersecretary of State Michael H. Armacost, in Manila as part of a two-week Asian tour, is to see Aquino on Tuesday.}

Several analysts said the government did not want to escalate the attache matter and cause a serious diplomatic rift with its key superpower benefactor, but also did not want to seem reluctant to act on an issue that has aroused intense nationalistic and anti-American passions here.

The Reagan administration's support of Aquino and the threat to cut off aid if she is toppled have been reiterated each time the government has faced a fresh threat. Centrist opposition leader Blas Ople calls Aquino "America's trophy of a rare foreign policy victory in the Third World."

American backing for Aquino has prompted speculation in anti-Aquino circles about a "constitutional coup," forcing Aquino from office but replacing her with the legally elected vice president, Salvador Laurel. Laurel, who is now in the United States, has already announced that he is available for the job. Such a move, according to Laurel, Ople and other opposition leaders, might be seen as a way to circumvent strong American condemnation of a coup and prevent an aid cutoff.

Platt, however, repeated last week that American aid would be cut in the case of a coup, and he called the "constitutional coup" variant "a contradiction in terms."

In a former colony protective of its independence, which was bestowed July 4, 1946, any hint of American involvement evokes strong nationalist feelings.