Accused Palestinian Killer Says He Blew Up Flight 103 : Terrorism: Follower of Abu Nidal stuns court with claim he planted bomb on Pan Am jet in 1988. Experts are skeptical.

An accused Palestinian assassin confessed Monday to the murder of 270 people, stunning a Beirut courtroom with an unsubstantiated claim that in 1988, he personally blew up Pan Am Flight 103 over Lockerbie, Scotland.

Lebanese prosecutors said they will investigate Youssef Shaaban’s claim but stressed that they doubted his confession. It reportedly came after the 29-year-old follower of terrorist leader Abu Nidal denied charges that he shot and killed a Jordanian diplomat near the diplomat’s Beirut home in January.

The Lockerbie bombing, one of the bloodiest terrorist attacks in recent years, remains a major international political issue. The American and British governments initially blamed Iran for the crime, then Syria, and finally insisted that two suspected senior Libyan intelligence agents were behind the bombing. They persuaded the U.N. Security Council to punish Libya with international sanctions in an attempt to force it to turn over the two men to stand trial in the United States or Britain.

On Monday, the lawyer for the two Libyan suspects--Abdel Basset Ali Megrahi and Lamen Khalifa Fhimah--applauded Shaaban’s confession in Beirut, asserting it proved his clients’ innocence. But British and American officials insisted that Libya still bears the blame for a bombing that stunned the world.

American counterterrorism officials said Monday that they had never ruled out a role by others besides the Libyans. “We’re going to follow up very hard on all leads, including this one, just to make sure we’ve left nothing unturned,” a senior official said.

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But counterterrorism experts, public and private, expressed deep suspicions. “There are enough inconsistencies to make us doubt him,” a senior U.S. official said.

Shaaban would have been only 23 at the time of the 1988 bombing. “That’s fairly young to have put together a complicated bomb and such a complicated operation all by himself,” the official added.

Also, Shaaban’s claim does not conform with Abu Nidal’s usual tactics. “He never went in for aviation terrorism, especially anything as sophisticated as this,” said Bruce Hoffman, a terrorism specialist at the RAND Corp.

American officials and terrorism specialists suggest that Shaaban’s claim may be part of a Libyan campaign to shift the blame from the two Libyans indicted by the United States and Scotland and, in turn, to get painful international economic sanctions lifted.

“It’s part of an operation. It’s deliberately exploiting the use of someone already going down for another crime--in this case the assassination of a Jordanian diplomat--to accept responsibility for something that he could not possibly have done,” said Vince Cannistraro, a former CIA terrorism specialist.

Relatives of the bombing victims were skeptical as well.

Jim Swire--chief spokesman and activist for families of British passengers killed when the Pan Am Boeing 747 exploded en route to New York over the Scottish village, killing all 259 people aboard and 11 more on the ground--said Shaaban’s assertion “should be regarded with grave suspicion.”

“It could be that he is seeking to attract what terrorists might regard as kudos for the Abu Nidal organization,” Swire said, referring to the Revolutionary Council of Fatah founded by the Palestinian activist.

Shaaban’s remarks--which the judge ordered stricken as irrelevant to the case, according to Reuters news service--reportedly came after Shaaban denied gunning down Jordan’s second-ranking diplomat in Beirut on Jan. 29. Shaaban’s public trial has become the centerpiece of a Lebanese government campaign to prove that Beirut’s decades of lawlessness are at an end.

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Times staff writer Fineman reported from Nicosia, Cyprus; special correspondent Raschka reported from Beirut. Times staff writer Robin Wright in Washington contributed to this report.