MANILA, OCT. 7 -- President Corazon Aquino today launched a crackdown on the media, closing three radio stations and ordering the investigation of a television station after receiving intelligence reports that various rebel military groups and opposition politicians had formed a new alliance to topple her government.

Aquino and her Cabinet received reports of an impending coup during a briefing by armed forces Chief of Staff Gen. Fidel Ramos, according to spokesmen. More than 1,000 troops with armored personnel carriers and tanks were deployed around the presidential palace to protect Aquino.

Officials said the planned coup is potentially a more serious uprising than the one in August, because the plotters had joined forces with factions in the military loyal to ousted president Ferdinand Marcos and with Eduardo Cojuangco, a powerful businessman allied with Marcos. Cojuangco now lives in exile in Los Angeles.

{Washington attorney John Chwat, saying he represents Cojuangco, released a statement tonight in which Cojuangco denied any role in a coup attempt and said, "The government should stop blaming others for the disastrous condition the country is in."}

Ramos accused two renegade colonels -- Gregorio (Gringo) Honasan and Reynaldo Cabauatan -- who led two earlier coup attempts, of involvement in the current plot.

{In Washington, State Department spokesman Charles Redman made a statement in support of Aquino, saying, "We are unalterably opposed to any effort to overthrow President Aquino's constitutional government." He said the closing of the radio stations was done in compliance with legislation pending in the Philippine Congress, adding, "It seems to me that that's something supported by the Philippine people through their elected representatives."

{Redman said the Philippine military "remains in a high state of alert," but added: "President Aquino is in charge. She's made a lot of progress . . . . She has difficult problems to address, but . . . we remain confident of her ability to address them."}

The broadcasting stations targeted in today's crackdown were accused of helping the coup plotters by broadcasting the views of anti-Aquino rebels. The closures marked the government's most drastic response yet to continuing coup threats.

Presidential press spokesman Teodoro Benigno said the three radio stations were "blatantly guilty of glorifying the enemies of government" by airing interviews with fugitive military officers who have been implicated in past plots to overthrow the government but have not been apprehended. He said the stations were "transmitting the propaganda of right-wing rebel groups."

Government officials also said they would investigate why the nation's Movie and Television Review and Classification Board allowed a Manila television station to broadcast a taped, hour-long interview tonight with Honasan, the leader of an unsuccessful Aug. 28 coup who is the object of a nationwide manhunt.

"This was not a live show," said Aquino's chief of staff Catalino Macaraig. "The board of censors could have stopped it."

Manuel Morato, chairman of the television board, said the military had seen a tape of the Honasan interview before it was aired and could have stopped it.

The moves against the media, coming from a government publicly committed to upholding press freedom, received support from congressional leaders. Jovito Salonga, the Senate president, introduced a controversial bill that would allow the government to close any broadcasting facility "in the event of invasion, rebellion or insurrection."

House Speaker Ramon Mitra said today, "That's what we fought the revolution for -- freedom to do these things. But that freedom has to have some responsibilities."

Today's actions against the media follow weeks of increasing frustration in the Malacanang presidential palace that fugitive rebel leaders, particularly Honasan and Cabauatan, have enjoyed almost unlimited access to the local and foreign media while eluding a police and military manhunt. The situation has raised widespread questions about how diligently the military was pursuing the rebels.

Interviews with Honasan have become an almost regular feature in Manila newspapers. Cabauatan, considered a supporter of Marcos, embarrassed the government last week when he held a press conference in the Makati business district of Manila. He talked to more than two dozen reporters for more than an hour.

News agencies today reported that Cabauatan held another news conference late last night on the grounds of the U.S. Clark Air Base, on northern Luzon island. A reporter for United Press International said he was driven through one of the main gates at the base and taken to a private house for a meeting with Cabauatan.

Spokesmen for Clark said they doubted the veracity of the report. But the base includes more than 2,000 private houses, mostly occupied by U.S. servicemen, and some officials said it was conceivable.

{In Washington, Redman said "we have no information about whether the colonel might have been present on some portion of the base outside of U.S. facilities." He called Cabauatan "a Marcos loyalist with an obvious interest in propagating disinformation."}

In the interview, Cabauatan reportedly said another coup attempt was imminent because "we have already infilitrated the palace and we have plenty of men there . . . . We are sure now that our next attempt will succeed because we have enough manpower or firepower."

An arrest order was issued for Cabauatan following a revolt in January by several hundred rebel officers who attacked military headquarters and Villamor Air base here. Cabauatan is believed to lead a force of a few hundred men.

Honasan, on the other hand, is believed to be leading more than a thousand men. He is thought to enjoy considerable sympathy within the armed forces, even among troops who nominally backed Aquino during the Aug. 28 coup.

In interviews last week, Honasan said he had spent most of his time since the coup traveling freely to military camps on Luzon Island, talking to the troops and shoring up his support in anticipation of another move, which he insisted would be "nonconfrontational."

Military officials have long suspected that Honasan's group might form a tactical anti-Aquino alliance with Cabauatan's smaller faction. Cabauatan told reporters last week he was supporting Honasan's efforts to replace Aquino with a new civilian-military junta.

Local analysts and foreign diplomats said the Aug. 28 coup came close to toppling Aquino, but lacked a civilian political component that could have stepped in to run the country. When Honasan and his supporters in the officer corps staged the February 1986 revolt that toppled Marcos, Aquino served as the political rallying point that generated the civilian backing for that coup.

It was unclear why Honasan, who was instrumental in toppling Marcos, would join forces with those wanting to bring back the deposed dictator. Some suggested that the announcement of the plot may have been part of a government disinformation campaign to discredit Honasan.

According to officials today, Honasan and Cabauatan may have joined forces with the old Marcos political machine, the KBL party, and with the opposition Grand Alliance for Democracy, a coalition of antigovernment politicians including Sen. Juan Ponce Enrile, the former defense minister and Honasan's mentor.

{From his exile home in Honolulu, Marcos said, "The alleged coup d'etat is a figment of the imagination of the Aquino administration. It is also an indication they are afraid of their own shadows," UPI reported.}

Late last month, Blas Ople, a former labor minister and supporter of the Grand Alliance, announced its plans to form a "shadow government" to be able to step into power should Aquino be forced from office. But he denied that the "shadow cabinet" was intended to be the missing civilian component of Honasan's military rebels.

Grand Alliance forces were boosted last month when Vice President Salvador Laurel announced that he was breaking from Aquino to become a critic of her government. Washington Post staff writer David B. Ottaway contributed to this report from Washington.