Phillipine President Ferdinand Marcos moved last night to soften a sudden weekend return to harsher measures of marital law by ordering the release of nearly 600 persons arrested in a peaceful protest march.

Marcos' action seemed motivated in part by his sensitively to foreign news coverage of the arrests, emphasized when one of his press aides called in two American reporters yesterday to express Marcos' disappointment over what he condidered one-sided news accounts. The prisoner release also represented another fine-tuning of opposing forces in Philippine politics, an art that Marcos has mastered during 5 1/2 years of martial law.

An official statement from Malacanang Palace said eight leaders of the Sunday march, including four candidates in Friday's National Assembly election, would remain in custody on sedition charges. The statement said the rest of the marchers, mostly young opposition campaign workers, included many "first offenders who probably did not know the full implications of their participation in the march."

The statement said the president ordered the mass release, expected today, "in accordance with the national policy of condiliation to bring together all the various factions in society."

Opposition forces that appeared to have polled more than a third of the vote in a hard-fought election for essembly seats from Manila loudly protested Sunday's mass arrest, the first action of its kind after months of a relatively relaxed political atmosphere here. Some observers called the arrests "overkill" and expressed surprise in particular that the March leader, Lorenzo Tanada, 79, a former senator and one of the most respected politicians in the country, had been detained.

After an election eve "noise barraae" demostration that the government said caused car damage and some injuries, Marcos warned that he would take "preventive and preemptive" action to fore stall any violent protests. He and his supporters also reacted angrily to foreign press reporting of opposition charges that ballot-boxes had been stuffed and ballots destroyed or falsified during the election.

Yesterday, the director of the Bureau of National and foreign information, Lorenzo J. Crus, called in Fox Butterfield of The New York Times and myself to express what he called the president's disappointment in our reporting.

Crus said he felt the government's side and not been given enough coverage and asked how long we planned to stay in the Philippines.

Several Marcos supporters have said he called the assembly election at least a year earlier than he wanted to because he saw a need to counter criticism of Philippine martial law in the United States. Marcos is negotiating a new military bases treaty with Washington that could bring $100 million more a year, and palace sources said he is concerned that the issue of human rights and free elections might stymie approval of the treaty in the U.S. Congress.

Marcos still appears anxious to cut off any real threat to the stability of his administration from opposition protesters, but he has made tentative moves to diffuse charges of cheating in the election. The government commission on elections has begun hearings on a few charges of abuses outside Manila, and some Marcos supporters are being allowed to air complaints of cheating against other candidates on the pro-Marcos ticket.

An important measure of how far Marcos will go in satisfying U.S. critics will be handling of the cases of the eights March leaders remaining in prison, and of former Senator Benigno Aquino, the country's most prominent political prisoner and the leader of the opposition.

The spokesman said the marchers who are to be rased could still be subject to trial on the sedition charges, but he said that the government would probably no prosecute "first offenders."

Marcos' initial decision to allow the mass arrests Sunday revealed how difficult he finds if to tolerate dissent and how doubful is his expressed plan to return the country eventually to full democracy. Yesterday's statement said the marchers "openly advocated the use of violence against the government." Earlier statements pointed to march placards saying, "Revolution, When?"

Since declaring martial law in 1972 after two terms as president that culminated in iwdespread violence and corruption, Marcos has successfully balanced military and business demands for stability against worker and peasant demand for social change. While jailing dissidents and hunting Communist guerrillas, he has effected some land reform and spread more social services into poor areas.

Friday's election was an attempt to balance the same demands for political stability against domestic and foreign appeals for more democracy. Some Marcos supporters here call the election a blunder and say he would be better off it he had not called it now. Yet, Marcos was careful that his own position of unchallenged power would be unaffected by the establishment of a new assembly. Block voting and the patronage system also guaranteed that nearly all the assemblu winners would be his supporters.

Still, with about 20 percent of the Manila returns counted, the opposition is showing a surprising 40 percent of the city's vote, which Marcos can use as another indication that he voting was relatively free. The assembly also helps legitimize the election of a successor to Marcos in case of his death, a weakness in the martial law system that had worried both his supporters and critics and many foreigh diplomats.

Reuter reported that military sources said security forces raided a Jesuit house of studies yesterday and carried off large quantities of documents. A spokesman said the papers belonged to Richardo Dong who was identified as an organizer of Sunday's march.