MANILA, OCT. 8 -- President Corazon Aquino's spokesman today defended a decision to close down three antigovernment radio stations, even as fresh doubt surfaced today over whether military warnings of an impending coup were deliberately exaggerated to counter propaganda of rebel soldiers.

A high-ranking government official, speaking anonymously, today said reports that various rebel military factions had linked up with opposition politicians to launch a "supercoup" were part of a sophisticated game of psychological warfare being waged by armed forces Chief of Staff Gen. Fidel Ramos.

This well-placed official said the intelligence reports Ramos cited yesterday to warn the Aquino Cabinet of the plot were actually old reports based on the observations of a "deep penetration" government agent who had infiltrated the ranks of rebel troops loyal to ousted President Ferdinand Marcos.

This official said Ramos used the old report to outline to the Cabinet a fresh coup plot that involved soldiers loyal to Marcos wearing civilian clothes making their way to Manila and receiving arms from caches around the city.

The official said Ramos chose to unveil the plot, and give it the appearance of immediacy, in part to counter the current media blitz being waged by renegade Col. Gregorio (Gringo) Honasan, leader of the Aug. 28 failed coup attempt, and Reynaldo Cabauatan, another fugitive officer linked to several past coup attempts. Both men, although the objects of manhunts, have been giving frequent interviews to reporters.

"They have their psy-war and now we have ours," this official said.

Meanwhile, Aquino made a surprise trip today to the Bicol region of the country, which has been the principal battleground in a new strategy by the communist New People's Army to focus their attacks on economic targets. Four bridges were totally or partially destroyed recently, isolating several small towns, and a passenger train was hijacked last month by hundreds of rebels.

In Camarines Sur, Aquino, making her first trip out of the capital since the Aug. 28 coup attempt, said, "I am not afraid of what will happen to me. What is important is that I see for myself what I can do for you."

Troops were placed on full alert following disclosure of the plot, and Malacanang presidential palace was surrounded by troops in full combat gear. The official said the stepped-up security was "an exercise that's good for the soldiers."

Journalists noted that security at the palace was considerably lighter today, just hours after the "impending coup" was announced.

Skepticism about the alleged coup threat was voiced today in the media and by opposition politicians.

Luis D. Beltran, a widely read columnist, wrote in today's Philippine Star that the so-called "Coup To End All Coups . . . is the stuff of which political horror stories are made."

"Perhaps it is only one of the personal nightmares of Aquino administration officials, and there really isn't any such plot in the offing," Beltran wrote. "The more cynical among us may say that this is the latest psychological warfare tactic dreamt up by administration propagandists who see it as a vehicle for unifying public support . . . behind the president, whose popularity has been slipping."

Sen. Juan Ponce Enrile, a leading figure in the loose opposition coalition called Grand Alliance for Democracy, dared Aquino today to arrest him or any other opposition leader if she had any solid evidence linking them to the latest coup plot, as the palace has alleged.

"If they have somebody in mind in the Grand Alliance, why don't they arrest these people?" Enrile said. "They can arrest Enrile . . . or somebody else if it is true."

Enrile warned that by closing the radio stations, Aquino was moving the country toward martial law.

Teodoro Benigno, Aquino's spokesman, defended the order to close the stations, saying, "The situation is not normal. The situation is {that} there is a warning of an impending coup."

"Have you listened to these radio stations?" Benigno said. "Have you found the filth and garbage they have been spreading? My God! If you did it to Marcos, you wouldn't last a day."