Philippine President Ferdinand Marcos cracked down yesterday on opponents of martial law as anti-Marcos groups protested cheating in the country's first election in more than six years of one-man rule.

"I have directed that if necessary, even before the beginning of any violent demonstrations, [the police and army] shall take anticipatory and preventive action, like arrests, confiscation of vehicles and prevention of any gathering of armed men," Marcos told a televised press conference.

The president said that all 21 members of the ticket headed by his wife, Imelda, that ran for seats in the new interim National Assembly from the greater Manila area had been elected. "It's a clean sweep," he said. Manila was the only area in the country where candidates from Marcos' New Society Movement faced significant opposition.

The leader of the opposition ticket in Manila, Benigno Aquino Jr., a former senator now in prison on charges of murder, placed 22nd, Marcos said. The lowest vote-getter on the government state will got 300,000 more than Aquino, Marcos said.

Police continued arrests of people from the opposition, including 52 who participated in an election eve demonstration, and searched for one opposition candidate, Charito Planas. Police who raided her home on Friday, election day, said they found "illegal arms and subversive literature." Marcos charged that Planas, an attorney and former martial law detainee, had sheltered leaders of the Communist New People's army during the campaign.

Marcos said he ordered arrests to begin midnight Thursday after an evening noise demonstration sponsored by the opposition. That protest, he said, caused damage to automobiles and at least one death. A spokesman for the opposition People's Power slate, popularly known as Laban, said the demonstration had been a protest against martial law and that he knew of no intentional damage. "They even broke my radio antenna, they were so happy to see me," said the spokesman, former congressman Joaquin Roces.

Police said they were on alert for another demonstration yesterday, announced in flyers distributed by a group called the Citizen's Movement for Freedom. By midnight, however, there had been no trouble, police said.

In election results from other parts of the country, more than a dozen independent candidates vying against Marcos-backed slates seemed close to winning seats in the 200-member assembly. Only one or two of the independents are considered outspoken opponents of martial law, however.

Roces said some defeated opposition candidates were having medical examinations yesterday in case they were arrested and authorities attempted to escape blame for injuries suffered. Others rested and waited for the vote count to finish. Aquino's wife, Cory, spent yesterday and last night in his room at Fort Bonifacio. She is allowed a conjugal visit each Saturday.

The opposition has charged massive ballot box stuffing by pro-marcos foces in Friday's voting. The government has rejected the charge and said the election was the cleanest in decades, pointing to the few precincts where the pro-Marcos slate lost. Reporters checking the polls Friday saw some areas where opposition poll-watchers had no complaints and others where ballots had been stolen or mutilated and tally sheets apparently falsified.

Marcos accused "subversives" in the opposition of trying "to sour up the atmosphere to further what they always claim is the ultimate aim, to establish a revolutionary situation.

"We have just demonstrated the fact that a small, active militant minority can wreck all the good intentions of the majority," Marcos said. "We must study exactly whether we should encourage any further experimentation on the elections."

Marcos' supporters have claimed he was forced into calling the election earlier than he wished by pressure from the U.S. government, which Marcos hopes will soon grant a large increase in compensation for use of military bases on Philippine soil.

Marcos permitted the opposition to campaign freely and allowed Aquino a national television appearance. Yet Marcos' victory seemed inevitable, probably more because of his enormous patronage power over thousands of local neighborhood leaders than because of any voter fraud.

Aquino and the other opposition members benefitted from the publicity given their arguments against martial law. Their showing in Manila, by some estimates as much as a third of the vote, was substantially higher than the 10 percent anti-Marcos vote in a previous martial law referendums.

Some Marcos supporters have gone so far as to compliment Aquino for refraining from personal attacks on Marcos and his wife and for conceding in public that martial law has done some good such as reducing crime.

Marcos has made no promises about releasing Aquino, however. He was jailed on the first day of martial law in September 1972. The charges of subversion, murder and arms possession against him now being reviewed by the supreme court. A death sentence from a military court has been temporarily set aside.

Members of Aquino's family want him to accept exile in the United States, where he has been offered a position as visiting scholar by Harvard Law School.