Thirty employes of a government vote-counting center walked off their jobs last night to protest what they said was the falsification of results from Friday's election contest between President Ferdinand Marcos and Corazon Aquino.

The walkout from the counting center of the government's Commission on Elections, a Marcos-appointed body known as Comelec, came as the center's tabulations showed Marcos holding a slim lead in unofficial returns. The dramatic protest was the most damaging example to date of massive election fraud engineered to keep Marcos in power, opposition leaders said.

Comelec officials said their count was put on hold this morning. No reason was given.

A rival count by an independent civic group known as Namfrel, which the Marcos government has been seeking to discredit, continued and put Aquino ahead by a substantial margin.

Under Philippine law, the formal canvassing of election returns will be done by the National Assembly, which is to meet later today. But the election commission and Namfrel have been conducting separate unofficial counts since the polls closed Friday. These counts were intended to establish a winner in the public mind and allay fears of manipulation if returns were delayed.

Sen. John F. Kerry (D-Mass.), a member of a group of 20 U.S. observers sent by President Reagan to monitor the election here, said, "These are the most damning comments I've heard and the most dramatic incident I witnessed since I came," referring to the accounts by the employes about the walkout. He said it would have "an enormous and very significant impact on my perceptions" of the election, and he indicated that the observer delegation headed by Sen. Richard G. Lugar (R-Ind.) would take the walkout into consideration.

Lugar, in a press conference before leaving for home today, said that his group had found "disturbing reports" of electoral abuse.

The director of the Comelec counting operation, Col. Pedro Baraoidan, a West Point graduate and U.S.-trained computer specialist, said at a breakfast that those who walked out had been his employes for 10 years at the National Computer Center, an organization under the control of the office of the president and located inside Manila's Camp Aguinaldo military complex.

He said that about 20 had walked out and accused them of being "hard-core opposition" without his knowledge and of hatching a plot to sabotage the Comelec count operation.

"I depended on these people, but little did I realize I was being set up," Baraoidan said. "I realize I've been naive about the whole thing."

He defended the Comelec count as being based on "hard documents" and said that he thought the employes who walked out were "liable for criminal charges" for having taken materials with them. The employes said they brought out evidence to prove their charges that the Comelec tally was being manipulated.

The walkout came amid rising confusion and growing political tension over charges of fraud and delays in the tally. Legislators of Marcos' ruling party said this morning that they would introduce a resolution in the National Assembly suspending all unofficial counts.

Cardinal Jaime Sin, archbishop of Manila, praised Namfrel and condemned "widespread disenfranchisement of qualified voters" in the election. He called on "all those in power, all those who are involved in the process of counting the vote . . . to act in the light of their conscience" and he called for an extension of the suspension of classes that Marcos had imposed for the elections..

A team of international observers yesterday said that they found numerous cases of fraud by supporters of Marcos. The group's co- leader, John Hume, said the group found no evidence of cheating by the opposition.

In an interview yesterday on ABC-TV, Lugar warned that the presidential election is "teetering on the brink of disaster." Referring to government indications that it will suspend unofficial counts, Lugar called on Marcos "to let the count continue."

Marcos, in back-to-back interviews on U.S. television yesterday, said that there is "no intent to cancel the elections because of fraud charges." He had indicated earlier that he was considering such a possibility. Appearing on NBC's "Meet the Press," Marcos also said he was "disappointed" at his showing so far in unofficial returns, but, he said, "this lowering of the votes for me was due to some anomalies."

He accused the Roman Catholic Church of denying him a landslide victory, saying priests had tried to dissuade people from voting for him.

He denied allegations of fraud or delay in the vote count, blaming instead stormy weather in the Philippines. "The seas are high, and naturally you cannot bring in the results from the precincts . . . and the rivers are swollen, and nobody can go through except in the helicopters." Manila's weather bureau reported fair weather in the region.

Last night as of 10:10 p.m. (9:10 a.m. Sunday EST), Namfrel said it had counted returns from 49 percent of the precincts and showed Aquino ahead with 5,576,319 votes to 4,806,166 for Marcos. It showed Aquino's running mate, Salvador Laurel, leading Arturo Tolentino 5,305,040 to 4,533,300.

The government Commission on Elections, however, with 28 percent of the precincts counted, had Marcos leading 3,056,236 to 2,903,348 as of 7 p.m. yesterday (6 a.m. Sunday EST). It also showed Tolentino ahead in the vice presidential race, 2,877,058 to 2,776,596. It had earlier showed Laurel in the lead.

Two other counts, conducted by progovernment newspapers and television stations, showed Marcos winning.

The capital appeared normal today with only one demonstration in progress at the Makati municipal hall by Aquino supporters who are concerned that electoral returns maybe stolen.

In the walkout, two representatives of the employes, all but two of whom were women, said early today that they left after a day of agonizing over the public posting of results that differed significantly from those they had tabulated. Many of the employes were sobbing and evidently frightened as they left the counting center and took refuge in a Roman Catholic church.

They were joined there by dozens of reporters, opposition supporters and several U.S. congressmen here to observe the elections.

The employes, most of them computer terminal operators, appeared before reporters at the church at about 1:45 a.m. after composing themselves for more than three hours. Although they were filmed and photographed, they declined to give their names, citing fears for their safety.

"We have walked out for purely professional reasons," said a spokeswoman for the group, one of more than 100 computer terminal operators recently hired for the "quick count" operation of the government body reponsible for overseeing Philippine elections. "We feel that we have been used."

She said "discrepancies" had appeared around midnight Saturday between the posted results and those the operators had processed.

"We noticed that the generated output was not the same values as we were inputing," she said.

A second spokeswoman, who described herself as a supervisor, said the falsifications favored one candidate over the other but declined to be more specific. Other employes told reporters privately that the mysterious results that initially aroused their suspicions had added more than 100,000 votes to Marcos' total.

"This is smoking-gun evidence" that Marcos' ruling party is trying to steal the election," said opposition lawyer Joker Arroyo. "This is the kind of evidence that breaks the lid open."

Brian Atwood, director of the National Democratic Institute for International Affairs in Washington and a member of the international delegation, said he thought the protesting Comelec employes were "the most credible witnesses I ever heard."

As the employes discussed what to do in a sanctuary of the Baclaran Church, the scene of a mass attended by Aquino yesterday, about 300 worshipers sang a patriotic song identified with the political opposition to Marcos.

Opposition campaign workers said the walkout had taken them by surprise and denied any involvement in it.

In a press statement, Comelec chairman Victorino Savellano said: "Recent statements made by Comelec volunteers questioning this counting process is a political attempt to sabotage our efforts. We are unaware of who these persons are or why they have had those claims. However, I can assure everyone that our doors remain open for all to see, and our tally sheets are beyond doubt."

Comelec member Jaime Opinion, in an apparent reference to the employes' walkout, said this morning on television that they had left because they could not stand pro-Aquino heckling that was being heard in the count center.

The government has kept up pressure on Namfrel, whose unofficial returns consistently show Aquino in the lead. Marcos on Saturday accused it of inflating her figures.

In a televised debate this morning with Namfrel chairman Jose Concepcion, Opinion angrily accused the group of reneging on an agreement to cooperate in compiling unofficial "quick counts" of the winner. He said it had withheld returns it was supposed to share with the commission.

Concepcion, speaking with equal emotion, displayed a casing from a bullet that he said had been fired in an incident of election violence. He eulogized a Namfrel volunteer who he said was killed by armed men who were trying to seize ballots.

The National Assembly is to meet later today to begin formal canvassing of election returns. By law, it has 15 days after it receives all the returns to declare a winner. But some officials have been quoted as saying that it might reach a conclusion as early as midweek.

Marcos' New Society Movement controls about two-thirds of the assembly's seats. A Namfrel spokesman said the group would comply.