A wave of terrorist bombings that culminated in an explosion during tonight's nationally televised opening ceremonies of an international convention here have put a damper on political accommodation and led to a new confrontation between President Ferdinand Marcos and his increasingly frustrated political opposition.

The blast suggests that at least some opposition groups formerly opposed to violence have now embraced terrorism as the only way of replacing Marcos.

Marcos publicly linked a prominent opposition leader to the previous bombings and was accused, in turn, of "McCarthyism." The bitter exchange has soured Marcos' relations with the opposition just as he was being given credit for seriously wanting to patch up old quarrels and open a dialogue.

Marcos, 63, has ruled the country for 14 years, the last eight of them under martial law, to the growing irritation of former senators and other political leaders who once supported him.

Several of his most severe critics said this week that they believed Marcos was moving toward a genuine acommodation by offering a dialogue and suggesting that he may lift martial law next March.

But the new exchanges related to the bombings have poisoned the air and prompted opposition leaders to reject the peace offerings.

One person has been killed and 58 injured in six bombings since late August. Police have arrested at least 10 suspects without publicly identifying them, and Information Minister Gregorio Cendana said tonight that more arrests will be made.

In one incident, a Philippine-born American businessman was critically wounded when a bomb he allegedly was working on blew up in his allegedly was working on blew up in his hotel room. Cendana also disclosed tonight that the man had agreed to turn state witness in the planned proceedings against the terrorists.

At a recent televised news conference, Marcos showed a picture of the man who is under arrest as a suspected terrorist, with former senator Jovito Salonga, a leading opposition figure once considered a likely presidential candidate. He did not specifically accuse Salonga but strongly implied he could be arrested.

Salonga angrily denied the implication, accused Marcos of "McCarthyism," and said the photo apparently was taken yers ago in the United States at a large social gathering.

Salonga himself has been the victim of political terrorism. His right arm was shattered by an explosion during a political rally in 1971.

In an interview this week, Salonga accused Marcos of attempting to use the incident to taint his moderate opposition forces with association with terrorism and destroy their usefulness as a political alternative to the Marcos-government.

Salonga believes the bombers may be friends and relatives of persons jailed for political activities, some of whom, he said, were tortured. He said they have abandoned political methods for terrorism out of frustration with Marcos' refusal to end martial law.

"I don't agree with their methods, but I can understand why they do it," Salonga said. The government is forcing them to "make a choice between condoning injustice or resorting to force."

Some opposition leaders believe Marcos has been prompted toward a spirit of accommodation because of an increase in the opposition ranks and its recently successful effort to bury internal differences and achieve a measure of unity. After last January's local elections, which featured renewed charges of corruption and ballot-box stuffing, Marcos' former political party, the Nationalists, went over to the opposition.

Then in August, eight political parties formed a "national convenant for freedom" that demanded an immediate end to "the Marcos dictatorship" and prompt dismantling of martial law.

The new alliance brought together both the Nationalist and Liberal parties, which had dominated the country's political life until Marcos imposed martial law in 1972 and formed his own party, the New Society Movement.

Confronted with this opposition unity and new agitation by students, labor, and church groups, Marcos began talking of a dialogue and renewed a pledge made last year to consider doing away with martial law.

He has hedged that pledge, however, by suggesting that martial law could not be lifted unless the sagging economy improves considerably and unless the long war against seccessionist Moslem movements in the southern Philipines is concluded successfully.

Many observers here doubt either of those conditions could be met quickly enough to permit a lifting of martial law by next spring.

Marcos' citics also point out that the rubber-stamp National Assembly has prepared legislation giving Marcos certain emergency powers to use in the event martial law is lifted.

The oppositon is sharply divided on whether substituting strong presidential emergency powers for martial law would be much of an improvement. Some point out it would at least do away with the military tribunals that now handle all political cases.

Others, including Salonga, believe the emergency powers would perpetuate authoritarian control while giving only the appearance of relaxing restraints to appease the public. "It would just be the same old dog with new colors," said Salonga.