One of the Palestinian hijackers of the cruise liner Achille Lauro today identified one of his fellow defendants, Yousef Magid Molqi, as the man who murdered Leon Klinghoffer, a wheelchair-bound American passenger on board.

Molqi's fellow defendants shouted in Arabic insults and threats against his life from their steel cells in the courtroom. And Ahmad Marouf Assadi, 24, one of the four men who is accused of hijacking the Achille Lauro last fall, said that Molqi told him immediate after Klinghoffer's death that he had killed the passenger.

"I saw he had blood on his shirt," Assadi said, talking at times in broken Italian, and at others, in Arabic, which was translated by a court interpreter. "I asked him what had happened and he said, 'I killed the American,' " Assadi said.

The American, Assadi's testimony made clear, was Klinghoffer, the man Molqi allegedly ordered wheeled out to the ship's stern from the salon, where the American and British passengers were being held as the ship stood off the coast of Syria on Oct. 8.

"We had agreed to kill no one, but he did it," Assadi said, his voice rising in emotion. "He did it without asking any of us. He did it all alone," he said.

Molqi, 23, interrogated yesterday by presiding Judge Lino Monteverde, denied killing the disabled American.

The young leader of the hijackers, who took over the Italian ship as it was sailing off the coast of Egypt, also retracted statements he made in a signed confession before the trial. He denied Klinghoffer was on board the cruise liner and asserted that charges that he was murdered was a "frame-up by the Americans and the Syrians."

Klinghoffer's body washed up on a Syrian beach less than 24 hours after being dumped with his wheelchair off the stern of the Achille Lauro. An autopsy, conducted in Italy after Syrian authorities turned over Klinghoffer's body, showed he had been shot at close range in the head and chest.

Assadi today confirmed every detail of his lengthy pretrial confession. Part of the confession stated that the hijacking had been planned, organized, armed and financed by Mohammed Abbas, the leader of the Palestine Liberation Front, a small, militant faction of Yasser Arafat's Palestine Liberation Organization.

Italian prosecutors have absolved Arafat of involvement in the hijacking and have said that Abbas had organized the incident in part to challenge Arafat's increasingly "soft line" toward using terrorism.

Because of the prosecution's report, judge Monteverde has been trying to establish in court the differences of attitude between Arafat and Abbas, whom Arafat brought into the PLO's executive committee in 1984.

Asked today about those differences, Assadi, an Arafat follower, said, "the difference between them is like sky and earth."

He said there was tension between Arafat and Abbas over strategy, but that because Arafat wanted to "control" Abbas and keep him from bolting to Arafat's Syrian-supported rivals, he could not oppose Abbas' actions.

Mowefaq Gandura, a defendant suspected of having helped make logistical and financial arrangements for the hijacking, testified today that he had nothing to do with the episode and had been arrested in Rome while on his way from Tunis to Beirut.

Before Assadi testified today, Gandura told the court he was a major in the PLO's secret police whose main responsibility was the defense of Palestinian refugee camps in Lebanon. He said when he was arrested his was on his way to Beirut on a special mission for Arafat: to help locate -- and free -- foreign hostages being held there by militiamen.

Aside from the five men being tried here in court in connection with the Achille Lauro hijacking last October, 10 other Arabs, including Abbas, are being tried in absentia for their alleged involvement in the ship piracy and Klinghoffer's murder. The trial, in the cruise liner's home port, is expected to last about two weeks.