Israeli security sources said tonight that they had never heard of the Palestinian guerrilla group, the "Martyrs of Palestine," named by the only survivor of yesterday's airport attack in Rome, but they said that it probably is a pseudonym for the Abu Nidal Fatah Revolutionary Council.

The Abu Nidal group, which broke away from the Palestine Liberation Organization's mainstream Fatah wing in the 1970s, has, since 1974, been the most ruthless opponent of PLO Chairman Yasser Arafat, the security sources noted.

They said it is common for established terrorist groups to adopt pseudonyms when launching attacks against civilians abroad, particularly when the attacks have been conducted in countries that have been sympathetic to the Palestinian nationalist cause.

The only surviving gunman in the Rome attack, identified by Italian authorities as Mohammed Sarham, reportedly claimed to be a member of the Martyrs of Palestine.

Israeli government officials involved in foreign policy, however, continued to maintain tonight that the burden of responsibility for the attacks is on the PLO umbrella organization and that it makes little difference which splinter organization is directly responsible for the attacks that killed 15 persons in Rome's Leonardo da Vinci Airport and three others in Vienna.

The lack of distinction, however, could have broad ramifications for the future of the Middle East peace process, Palestinian sources here said tonight.

Noting that Abu Nidal, a nom de guerre for Sabri Banna, has been under a death sentence decreed by Arafat's Fatah wing of the PLO, East Jerusalem Palestinian leader Hanna Siniora said, "Those who carried out these attacks are trying to undermine the peace process. They are misled and they are causing great harm to the image of Palestinians."

Siniora, editor of the pro-PLO Arabic daily newspaper, Al-Fajr, was nominated by Arafat to the proposed joint Jordanian-PLO delegation that Jordan's King Hussein wants to negotiate a comprehensive Middle East peace with Israel.

Siniora is one of only two nominees to the delegation who have been declared acceptable by Israeli Prime Minister Shimon Peres.

"The policy of the Israeli government is to try to damage the PLO's role in the peace process by not differentiating between Fatah and those extremist terrorist groups that are encouraged by sources outside the PLO," Siniora said in a telephone interview.

He said the Abu Nidal group, which is also suspected by Israel, Egypt and the United States of being responsible for last month's hijacking of an Egyptair jetliner to Malta -- leaving more than 50 passengers dead -- is controlled by Syria and receives support from Libya.

Abu Nidal originally founded his group as the Black June Revolutionary Council, and later changed the name to the Fatah Revolutionary Council when he openly vowed to assassinate Arafat and other leaders of the mainstream Fatah group. He reportedly was expelled from Baghdad two years ago, and has been reported since then to be operating from Syria and Libya.

Israeli security sources claim that Abu Nidal's group is the major Syrian-sponsored Palestinian guerrilla organization now actively conducting terrorist operations in Europe. They said that if Abu Nidal was responsible for ordering yesterday's airport attacks, it probably was at the behest of Syrian President Hafez Assad, who, the Israeli sources claim, would have a dual motive of undermining any role for Arafat in the peace process while diverting attention from the current crisis over the Syrian deployment of surface-to-air missiles in central Lebanon's Bekaa Valley along the Damascus-Beirut highway.

Israel's science minister, Gideon Patt, was quoted by Israel Radio tonight as saying that Israel would attack the Syrian missiles if diplomatic efforts failed to persuade Damascus to pull them back. Despite these comments, however, the Israeli government continued to play down the idea that any immediate confrontation with Syria was developing over the antiaircraft missiles. Syria, for its part, said it was on a "collision course" with Israel.

While PLO spokesmen in Tunis and Rome denied that the organization was responsible for the airport attacks, anonymous callers claiming to represent Abu Nidal's group have claimed that it was behind the attacks.

Siniora, noting Arafat's declaration last month in Cairo that the PLO would not participate in attacks against civilians outside of Israel and the territories it occupied in the 1967 war, said tonight, "The PLO condemns -- and I condemn -- those misled people who are causing damage to the PLO and the image of all Palestinians . . . . They are playing into the hands of the Israeli policy of stereotyping the PLO and all Palestinians as terrorists."

Israeli officials, however, said there could be no distinction between subgroups of the PLO, and suggested that the two airport attacks, coupled with the October hijacking of the Italian cruise ship Achille Lauro, had ruled Arafat and his organization out of any role in the Middle East peace process.

"It all leads to one thing, and that is Palestinian terrorism. You can call it Jibril terrorism. You can call it Hawatmeh terrorism. You can call it Arafat terrorism. But it is still Palestinian terrorism," an official of the Foreign Ministry said tonight.

He was referring to Ahmed Jibril, leader of the splinter Popular Front for the Liberation of Palestine-General Command, and Nayef Hawatmeh, head of the Syrian-based Democratic Front for the Liberation of Palestine.

"We don't know about their identity, but for us it makes no difference. It all leads to the fact that Palestinian terrorism is continuing," said the Foreign Ministry official, who asked not to be identified.

When asked whether the distinction was not relevant in terms of which guerrilla group Israel might direct retaliatory strikes against, the official replied, "We don't speak in terms of retaliation. We speak in terms of fighting terrorism wherever is necessary and whenever is necessary."

The official said the implications for the peace process of the lack of distinction between PLO subgroups were irrelevant because Israel's stated policy has been not to negotiate under any circumstances with any PLO members. He noted also that it is the declared policy of the United States not to talk with any PLO group that does not accept U.N. resolutions 242 and 338, which implicitly recognize Israel's right to exist within secure borders, and with any Palestinian group that does not renounce all forms of terrorism.