The trial of the accused hijackers of the Italian cruise liner Achille Lauro opened here today with a defense motion that Foreign Minister Giulio Andreotti be called to testify on the reasons why the government let the alleged mastermind of the hijacking, Palestinian leader Mohammed Abbas, leave Italy last fall.

In iron cages lined with bullet-proof glass in the heavily guarded, bunker-like basement courtroom, were five of the 15 accused -- three of the four alleged hijackers and two other Arabs accused of aiding and abetting the crime last October, in which 383 passengers and crew were taken hostage and an elderly wheelchair-bound American, Leon Klinghoffer, was killed.

Despite stringent security checks, four neatly dressed West Germans who had entered as spectators interrupted the trial with a noisy demonstration, shouting "Long live Palestine," and expressing support for "the Palestinian revolution."

Police quickly seized the three men and a woman and dragged them from the courtroom. Authorities later charged them with trying to distribute leaflets that defended criminal actions, United Press International reported.

Besides the five defendants present for the trial, 10 others accused of planning and aiding the seizure of the Italian liner on the high seas off Egypt last Oct. 7 -- including Abbas, head of a small Palestinian organization, the Front for the Liberation of Palestine -- are being tried in absentia since they are not in Italian custody. The fourth alleged hijacker, Bassam Asher, is to be tried later in juvenile court because he was 17 at the time of the crime.

All the defendants are charged with murder, hijacking, belonging to an armed band and aiding and abetting a crime. Defense lawyer Gianfranco Pagano said that the accused hijackers would not deny their participation in the crime but would stand by the Nuremberg defense that they were mere soldiers in a war, following orders.

Chief Judge Lino Monteverde devoted the first day's session to procedural questions and listening to defense motions, including the one on Andreotti's requested appearance as a witness.

After deliberating almost three hours behind closed doors, Monteverde rejected all but the Andreotti motion. Chief among those rejected was a contention that the Italian court had no jurisdiction in the case because the Egyptian plane carrying the hijackers had been intercepted by U.S. warplanes as it was flying them from Egypt, where they had surrendered, to Tunis, where the Palestinian Liberation Organization has its headquarters.

Monteverde said he would reserve judgment on whether to call Andreotti until later in the trial, which court officials said they hoped would last no more than two weeks.

Italy's decision to free Abbas has been highly controversial and nearly brought down the government. After Abbas, a key aide -- also being tried in absentia -- and the four hijackers were forced by U.S. planes to fly to Italy last October, the Egyptian plane landed at a NATO base on Sicily. There, it was immediately surrounded by Italian troops and U.S. commandos.

Because Abbas said that his only role was that of a mediator for PLO leader Yasser Arafat to end the hijacking, and because the Egyptian government claimed the EgyptAir jet was on an official government mission and therefore covered by extraterritorial status, Italian authorities took only the four hijackers into custody, allowing Abbas and his deputy, Abul Oz, to leave Italy on a Yugoslav airliner.

Prime Minister Bettino Craxi argued at the time that Abbas was released because no solid proof had been presented to Italy that would have justified his detention under Italian law. That position was sustained in the 115-page prosecutor's indictment that forms the basis of the current trial.

That document, however, said that after Abbas left Italy, a conclusive case of his guilt emerged from intelligence intercepts of radio conversations he had with the hijackers when he was talking them into surrendering, and from confessions of at least two of the alleged hijackers.

The main defendants in court today were Yousef Magid Molqi, 23, a Jordanian-born Palestinian who is accused of leading the hijackers aboard the Achille Lauro and who reportedly has confessed to shooting Klinghoffer; Ibrahim Abdel-Latif Fataier, 21, a Palestinian born in Lebanon who allegedly was Molqi's deputy; and Ahmad Marouf Assadi, 24, a Damascus-born Palestinian who grew up in Beirut and who, since his arrest, reportedly has been cooperating with authorities.

Also in the dock is Mohammed Issa Abbas, 25, a distant cousin of Mohammed Abbas. He had been arrested on other charges in Genoa before the Achille Lauro sailed and has since been accused of bringing to Italy from Tunisia the four Kalashnikov rifles and four hand grenades used by the hijackers in capturing the ship.

The fifth man in court today was Mohammed Gandour, 37, who was arrested in Rome last September, almost a month before the hijacking, for possession of fake documents. He has been linked to the Achille Lauro operation as a courier and financier of the hijackers. He was reputed to be close to a mysterious Greek, Petros Floros, of Athens, who was added as a defendant today on charges of aiding the hijacking. Prosecutor Luigi Carli said a warrant had been issued for Petros and an extradition request sent to Athens.