Ferdinand Marcos and Corazon Aquino staged rival swearing-in ceremonies for the disputed office of president of the Philippines Tuesday as rebel military forces supporting Aquino appeared to tighten their hold on power in the capital.

Aquino immediately named the two men who led the rebellion against Marcos' rule as her defense minister and armed forces chief of staff.

Marcos, who staged his ceremony inside the Malacanang presidential palace, the traditional seat of government here, vowed to continue his fight to stay in power.

There were reports of scattered violence as the tense, three-day-old military standoff between the rebel forces who have declared their support for Aquino and the loyalists still backing Marcos continued in the streets of Manila, which were clogged with hundreds of thousands of civilians who have come out to oppose Marcos.

The rebel-controlled television station in Manila, which was captured from the government on Monday, carried a report that a pro-Marcos column of 10 tanks headed into the city from the north had been "neutralized" by rebel helicopter gunships. There was no independent confirmation of this report.

Outside Malacanang Palace, troops backing Marcos fired on a crowd of protesters early Tuesday, wounding several, and crowds supporting Aquino continued to fill streets in strategic locations around the capital to prevent loyalist troops from attacking rebel-held installations.

There were also reports of heavy shooting around the privately owned television station that Marcos forces still control. The station was televising Marcos' inauguration at noon Manila time (11 p.m. EST Monday) when the screen suddenly went blank. The station announced that it had lost its link to Malacanang Palace and began showing a John Wayne film.

The presidential palace said later that Marcos had been sworn in for his fourth term by Supreme Court Chief Justice Ramon Aquino before several thousand cheering supporters, who had walked to the ceremony through barbed wire barricades that surround the palace. As they entered, they were heckled by Aquino supporters.

Marcos' running mate, Arturo Tolentino, did not appear at Marcos' swearing-in ceremony to take his oath of office. Tolentino, known as a political maverick who often criticized Marcos' policies, has been seen seldom since the Feb. 7 election that was marred by reports of massive fraud.

"We will overcome," Marcos said in his inaugural address to a roar of approval from supporters. "I can only promise that the powers of the presidency will be used in order to free our people from the bondage of old weaknesses and vices."

Marcos asserts that he won the national elections, but Aquino claims that the Marcos camp committed massive fraud in an effort to steal the presidency from her by falsifying vote returns.

Aquino was sworn in by Supreme Court Justice Claudio Teehankee at an exclusive sports club in suburban Quezon City. She called on the people "not to relax but to be more vigilant," adding "those who have not done anything against the interest of the people have nothing to fear."

She was protected by rebel soldiers clad in rumpled fatigues and carrying automatic weapons -- veterans of a struggle to establish control over the armed forces and strip Marcos of power.

In her first official act, she appointed Salvador Laurel, her running mate in this month's elections, as prime minister, Juan Ponce Enrile as defense minister and rebel leader Fidel Ramos as a full general and chief of staff.

Before she was sworn in, a proclamation signed by about 60 opposition legislators in the 190-member National Assembly was read. It said: "We proclaim Corazon Aquino and Salvador Laurel the duly elected president and vice president respectively, entitled to the recognition, obedience and allegiance of the Philippine people."

Aquino and the aides accompanying her at the oath-taking ceremony declined to discuss how they would go about taking control of the government. She indicated that she was establishing a series of special task forces to operate as ministries, but she did not name ministers to head them.

Enrile, asked on ABC-TV's "Nightline" if he expected Marcos to step down, said: "I think in the end it is the only option available to him unless he is willing to do what he says and that is to die inside the palace." He also indicated that the rebel forces would be willing to let Marcos go into exile abroad.

In a related development, an independent poll-watching group, the National Movement for Free Elections (Namfrel) issued its final tabulation Tuesday, giving Aquino a 782,000 margin of victory in the Feb. 7 balloting. Namfrel's tally of 7,835,070 votes for Aquino came from 70 percent of the country's precincts. The group said it could not vouch for the reliability of the other 30 percent.

Tensions in Manila and elsewhere remained high with unconfirmed reports by the rebel television that pro-Marcos troops were firing on crowds from a television transmission tower in Quezon City. But local residents said the troops had been firing into the air and could not confirm rebel reports of one dead and several wounded in the incident.

In the third day of the open rebellion of much of the military and government against Marcos' attempt to hold on to his 20-year rule, there were clashes Monday at the government television and radio station and rebel helicopters strafed Villamor Air Base, next to Manila's international airport, but only scattered casualties were reported.

Diplomatic sources confirmed reports from rebel officers that Villamor Air Base and the neighborring Manila airport had been secured by rebel forces. Rebel officers also claimed the defection of senior commanders known as Marcos loyalists, but these could not be confirmed immediately.

"It's going Cory's way," said one diplomat, referring to Aquino by her nickname. "A bit of psychological warfare is being waged, but there's no doubt that more people are going over" to the rebels.

The rest of the country appeared largely quiet. In Cagayan de Oro, in Mindanao in the south, rival military units postured and went on alert, but elsewhere in the provinces, most Filipinos appeared to be watching events in the capital.

As they had in a dramatic confrontation here on Sunday, crowds responding to appeals by the Roman Catholic Church and opposition leaders to demonstrate nonviolent "people's power" again prevented an advance by an armored column attempting to recapture the government's broadcasting facilities.

From inside his well-guarded palace, Marcos, 68, declared an ineffectual curfew and, saying that his family was "cowering in terror" in fear of attack, appealed to citizens to come to his defense.

Aquino, 53, the widow of assassinated opposition leader Benigno Aquino, spent most of Monday meeting with aides and going over documents for the proclamation of her new government. She then spoke briefly to the tens of thousands of supporters gathered at Camp Crame, the rebel military headquarters, telling them, "This is the first time in history that the civilian population has protected the military. Please keep vigil here."

Later, in a telephone interview with a television station, Aquino, speaking from her home in Quezon City, appealed to the country "to please desist from killing innocent people."

"We have gone through this with as little bloodshed as possible," she said, and she called on "all those who are backing Mr. Marcos to consider that so many of our countrymen have broken away from the Marcos government."

As the sound of gunfire could be heard in the background, Aquino told the television reporter that "right now" there was a firefight in the vicinity, and "my security are hurrying me out."

The defection Saturday of Enrile and Ramos brought the long-simmering dispute with Marcos over alleged election irregularities to a climax.

Hospital officials said eight persons were wounded in the shooting outside Marcos' palace and several others were injured in attempting to flee the violence.

Among the victims was Melinda Liu, Newsweek magazine's Asia regional editor, who was slightly wounded in the right leg by a bullet fragment. Liu said after being treated and released from a hospital that the violence was touched off when someone in a jeering crowd of protesters set off firecrackers near a barbed-wire barricade manned by loyalist troops.

Several dozen of the jittery troops then started firing their M16 rifles -- mostly into the air -- to disperse the protesters, Liu said. But some of the soldiers fired into the fleeing crowd, she said, wounding several people.

At midday Tuesday, an independent radio station broadcast an appeal for blood donations to help someone who had been severely injured in fighting around the Marcos-held television tower.

At about the same time, the same radio station broadcast an account of a shoot-out at a police station in the Makati financial district in which three hostages taken by eight unidentified armed men where killed in cross fire. This report was not confirmed.

Increasingly isolated at home and abroad, Marcos appears unable to stem a rapid unraveling of his authority.

In clashes Monday, the rebels took over the government television and radio station in Manila after a brief firefight with about 15 loyalist soldiers and later defended it from attempts to recapture it.

In the latest attempt around midnight, huge crowds responding to Roman Catholic Church and opposition calls to demonstrate nonviolent "people's power" stymied the advance toward the station of seven armored personnel carriers bearing loyalist troops.

A least a dozen junior officers of the elite Scout Rangers deserted on the way to the station, and the unit had to turn back. The officers later showed up at rebel headquarters and declared their support for the growing mutiny.

The leaders of the rebel troops -- Enrile and Ramos -- early Tuesday announced the latest in a continuing series of military and political defections that appeared to be building momentum for a middle-of-the-road revolution against Marcos.

Ramos said the Philippine Military Academy announced its "overwhelming support for the Enrile-Ramos camp" in a letter delivered to the rebel base at Camp Crame, on the eastern outskirts of Manila.

Ramos and Enrile said they now have the allegience of more than half the 250,000-strong Philippine armed forces, an estimate that western diplomats termed "plausible" but that could not be confirmed.

Three days after the military mutiny against Marcos, the leaders of the rival government now have to compete with Marcos for the loyalties of provincial officials and the rest of the Philippine armed forces.

The rival government already appears to have the support of the Reagan administration, which Monday called for a "peaceful transition to a new government."

Aquino spokesman Rene Saguisag read the text of President Reagan's statement at a news conference, and opposition backers burst into applause. Saguisag called the statement "the functional equivalent of recognition" for Aquino's provisional government.

Marcos did not respond publicly to the statement, but he had told U.S. Ambassador Stephen Bosworth on Monday that he had no intention of stepping down. He called on supporters to gather at his presidential palace to be issued weapons.

"I am fit and strong and quite ready to go to combat if that is necessary," Marcos said in a statement televised by a private channel owned by a close associate. He added that his "sniper rifle" was at the ready "in case it is necessary to protect my family."

The election was marred by massive vote-buying, fraud and violence perpetrated largely by Marcos' ruling party, according to U.S. and other election observers.

"What we call a new government is effectively a revolutionary government," said opposition legislator Luis Villafuerte, since constitutional rules would not be strictly followed.

Ramon Mitra, an opposition member of the National Assembly, said that Rene Cayatano, a leading pro-Marcos legislator, was encouraging fellow members of Marcos' ruling New Society Movement to support the new government, The Associated Press reported.

Marcos, showing signs of losing touch with the reality of a unique but unmistakable revolution outside his palace, contested the opposition move on legal grounds.

"What can they do without a quorum?" he asked in one radio interview. He called the opposition's ignoring of the rules of parliament for the proclamation of Aquino "usurpation of public authority and possibly rebellion, subversion."

He said that "the whole thing is completely illegal and unconstitutional and against the election code and other codes including the criminal code. We will file the cases against those concerned and have them arrested as soon as we are able to do so."

Marcos added, "We are still in control of the situation." But he conceded later that the current crisis "is a matter of survival" for him. "Now I am fighting for the life of our country and also fighting for my own life," he said.

Ramos, a West Point graduate, spoke to crowds outside Camp Crame and told them, "We have succeeded militarily despite overwhelming odds." But, he said, "We have been successful not so much because of military action but because of 'people's power.' "

Ramos said that "the military situation is under control," although his troops were "still mopping up and consolidating in some areas."

However, rebel officers were not taking lightly the prospect of attacks by loyalist forces and repeatedly broadcast appeals to their comrades-in-arms not to unleash a "bloody struggle."