Two of the top military figures in the Philippines rebelled against the leadership of President Ferdinand Marcos yesterday, seized control of the Defense Ministry and called for Marcos to step aside in favor of Corazon Aquino, his election challenger.

Marcos charged in a television address from his heavily guarded Malacanang Palace that troops loyal to him had foiled a coup attempt led by Defense Minister Juan Ponce Enrile and Lt. Gen. Fidel Ramos, the acting armed forces chief of staff, in which he and his wife, Imelda, had been targets for assassination.

But as the day wore on, Marcos, in another television statement, appeared to soften his accusations against Enrile and Ramos, saying they may not have been directly linked to the alleged plot.

In three separate television appearances, Marcos called for a peaceful resolution of the confrontation but warned that loyalist troops would "liquidate" the rebel forces in a bloody showdown if necessary.

Cardinal Jaime Sin, a key figure in the Philippines' rapidly escalating political crisis, issued an appeal over the Roman Catholic Church's Radio Veritas for civilians to gather at Camp Aguinaldo, home of the Defense Ministry on the outskirts of Manila, to support and protect Ramos and Enrile. Thousands responded to his message.

The prospect of a face-off between two military forces, with large numbers of civilians positioned between them, presented the gravest threat yet to the embattled Marcos, whose claim of victory in the Feb. 7 election has been subjected to escalating challenges of fraud.

Enrile, in announcing his and Ramos' support for Aquino, said yesterday that he had faced a "moral dilemma" because of massive cheating in the election. Marcos is scheduled to be inaugurated for a new term on Tuesday, and he said he would go ahead with the inauguration as planned.

Marcos, in his nationally televised announcement early this morning, said that "the situation is under control." By late morning Marcos had presented four officers on television who offered confessions to having participated in some sort of coup plot. One said that he and his colleagues had hoped to capture Marcos and force him to resign but had not intended to kill him.

At midday, appearing for the third time on television, with senior officers seated behind him, Marcos asserted that he had received pledges of support from key commanders and said there was no danger of the rebellion spreading. He said the two camps were surrounded by loyalist troops, but there has been no sign of pro-Marcos troops near the camps.

Marcos, repeating earlier claims that he could crush the rebels, expressed somewhat greater willingness to pursue what he said were "off-and-on negotiations" with the mutineers, and he restated his intention to end the rebellion without bloodshed.

In one of his earlier appearances he had warned that the rebels "can be easily wiped out with simple artillery and tank fire" and asserted that all military service commanders remained loyal to him. He said he believed the alleged plot was encouraged and supported by the political opposition, but he offered no evidence.

Aquino, visiting the city of Cebu in the central Philippines to promote a postelection campaign against Marcos, moved to a "safe and secure" location, opposition leaders in Manila said.

Enrile and Ramos denied that they had planned a coup but said they were defending themselves against an expected assault. They made the statements in a joint press conference in the heavily guarded Ministry of National Defense building.

Enrile said later in a second news conference that Aquino had called him from Cebu and asked "how we were doing and what was happening. . . . She asked me what she could do, and I told her, 'just pray for us.' "

He said that as recently as yesterday morning he had been publicly defending the Marcos government at a breakfast forum.

Both Enrile and Ramos warned that unless the showdown is resolved peacefully, the ultimate beneficiaries could be the Communist guerrillas of the New People's Army who have been waging a "people's war" in the countryside.

Members of the armed forces reformist movement, clad in combat gear and carrying automatic weapons, secured the building and said they had control of both Camp Aguinaldo and a neighboring base, Camp Crame, Ramos' headquarters.

There were no immediate reports of shooting between the two sides. Both called for negotiations as a tense standoff developed.

After the announcement of the mutiny, several other Philippine leaders resigned, including Jose Roilo Golez, the postmaster general, and Supreme Court Justice Nestor Alampay, Radio Veritas reported, according to United Press International.

The key to the outcome, military sources said, would be the support of other military units in the capital and the provinces, but the intentions of these units were not immediately clear. Enrile said early today that "we have an understanding" with Gen. Fabian Ver, a trusted Marcos loyalist who ostensibly retired as armed forces chief of staff last Sunday, that no troop movements would be ordered by either side and that negotiations would go ahead today.

Enrile and Ramos refused to say how many troops they had under them, but they contended that further support was available. Conflicting claims of support could not be independently assessed. A few hundred soldiers appeared to be in the vicinity of the Defense Ministry building inside the camp, and at one point supplies of additional arms and ammunition arrived by helicopter.

"We'll stay here until we are all killed," said Enrile, who has served in Marcos' Cabinet for 20 years. He added, "If he Marcos kills all of us, the Filipino people will react violently."

Early this morning, Cardinal Sin, the archbishop of Manila, threw the weight of the powerful Roman Catholic Church behind Enrile and Ramos, whom he called "our two good friends." Several thousand people responded to his appeal to gather at Camp Aguinaldo and kept a vigil into the early hours of this morning. Sin also appealed to soldiers on both sides to avoid bloodshed.

The crowds sang hymns and patriotic songs as dawn broke and a priest offered communion wafers.

Central Manila was calm this morning, with the usual Sunday crowds of joggers on the city's bayside boulevard. A solitary police car guarded the driveway of the U.S. Embassy.

The mutiny developed shortly after the departure from the Philippines yesterday of U.S. presidential envoy Philip Habib after a week-long fact-finding visit to assess the situation in the country following the election, which was marred by widespread fraud and violence. Aquino has launched a national nonviolent campaign to unseat Marcos through demonstrations, civil disobedience, strikes and boycotts.

Enrile said the departure of Habib had nothing to do with the actions of the reformist troops. He said he talked to Habib earlier during the U.S. envoy's visit and warned him about splits in the military. He said that he had informed U.S. Ambassador Stephen Bosworth and the Japanese ambassador of the situation by telephone. Enrile said he had not received an offer of support from either and insisted that "We are not involved with any foreign power."

He said Bosworth had asked whether there was any fighting and said he would communicate with the U.S. government. While the news conference of Ramos and Enrile was in progress, a U.S. military attache arrived at the Defense Ministry building at Camp Aguinaldo to talk to reformist officers, but he refused to speak with reporters.

Enrile said at the news conference that the mutiny developed after he received word of a plan to arrest him and members of the group of reformist military officers yesterday. He said members of the Presidential Security Command based at Malacanang were to make the arrests. However, he said, reformist officers took him from his house and brought him to the Defense Ministry before the plan could be carried out.

Enrile said he had heard of a plan in the Malacanang Palace to "arrest all the leaders of the opposition and some members of parliament." He said a "hit list" of opposition leaders had been prepared. "I am calling on all decent elements in the Cabinet, all decent soldiers . . . to wake up and support this movement," Enrile said.

He added, "I am morally convinced that it was Mrs. Aquino who was elected by the Filipino people" in the disputed election. "We are committed to support her." Enrile said it was "about time that the president heed the clamor of the people that he must step down."

Opposition figures began arriving at the Defense Ministry this morning, among them Aquino adviser Jaime Ongpin and her brother-in-law, Agapito Aquino. Ongpin said Aquino had been advised to remain in Cebu for security reasons.

"It's time for Washington to do something decisive," Ongpin said. He suggested that the United States ask Marcos to "do the statesman-like thing" and step down.

Opposition leaders said they planned to organize a vigil of thousands to guard the entrances to the two camps to prevent any attacks.

Enrile, wearing blue jeans, running shoes and an olive drab army windbreaker over a flak jacket, told reporters that he had faced a "moral dilemma" because of massive cheating in the election and a railroading of Marcos' reelection by the National Assembly, in which he sits.

He said that "in my own region we cheated in the election to the extent of 350,000 votes" for Marcos.

Enrile said that Marcos had "called me over the phone and asked me to . . . change the results in some provinces in my area." He denied that he personally participated in election fraud in the northern region, too, which includes six provinces, but he said that other loyalists had.

Enrile and Ramos stopped short of posing Marcos' resignation as a demand or condition in negotiations, but they said that he "should follow the will of the people" by stepping down voluntarily.

"For my part, we are withdrawing our support for Mr. Marcos and all of his cohorts," said Ramos, a West Point graduate and distant relative of Marcos who has served in the armed forces for 39 years. He said he and the troops following him no longer consider Marcos the "duly constituted" president.

Ramos added, "I am calling on all members of the armed forces of the Philippines and the . . . national police to disobey all illegal orders." He defined these as attacking the reformists, firing on civilians and arresting opposition leaders.

Ramos said Marcos had been "fooling" him and the world when he announced Ver's retirement last Sunday and named Ramos acting chief of staff. He also complained that his efforts to clean up corruption in the military had been sidetracked by Marcos.

More than six hours after the mutiny began, Marcos appeared on television in his palace office to deny that any arrest warrants had been issued for Enrile, Ramos or their followers. He claimed their actions stemmed from "an aborted coup d'etat and assassination plot against the president and the first lady" that was supposed to be launched shortly after midnight.

Marcos earlier presented two alleged conspirators who confessed to involvement in the purported plot. One, Army Capt. Edgardo Morales, was described as "an escort officer of the first lady." Morales identified the leader of the alleged plot as Col. Gregorio Honasan, Enrile's chief security officer.

Marcos said the purported plot called for a four-pronged armed attack on the presidential palace but that three of four battalions involved had been neutralized. He said Gen. Ver and his son, Col. Erwin Ver, the head of the Presidential Security Command, as well as Marcos' son, Ferdinand Marcos Jr., had discovered the alleged plot. He said it involved 1,000 troops, half of whom made up the attack force.

Marcos called on Enrile and Ramos to "stop this stupidity and surrender so we may negotiate exactly what should be done." He added, "If there were to be any fighting it would be a bloody mess. It would mean the liquidation of all the men in that corner of Camp Aguinaldo."

In reply to reporters' questions, Marcos said that stepping down was "out of the question."

Appearing on television again after 1 a.m. today, Marcos said he hoped that "we will not have to go on to any hostile counteraction to stop this. I would rather that we talk than shoot at each other."

Addressing the rebels, Marcos said, "I inform you that you are very vulnerable to artillery and tank attack. We know you have no defense against these weapons. We do not want anybody hurt."

Enrile replied, "We are no longer afraid to die because enough is enough. Mr. President, I think you know that your time is up."

At Camp Aguinaldo, the troops loyal to Enrile and Ramos appeared to be in an exhilarated mood as they embraced new arrivals. Among those who came to show their support were retired chief of staff Gen. Romeo Espino and the customs commissioner, Brig. Gen. Ramon Farolan