The Arab terrorist group that hijacked the Italian cruise liner Achille Lauro last year was personally selected and directed by Palestinian leader Mohammed Abbas and trained in one of his camps in Algeria before being sent from Tunisia to Italy to seize the vessel, according to a report prepared by Italian prosecutors.

The 115-page report, which is to form the basis of the government's case against four alleged hijackers and 11 other Arabs accused of involvement in the case, is Italy's most authoritative account to date of the investigation into the spectacular hijacking. It was made available today to The Washington Post.

The trial, on charges including the hijacking and the murder of Leon Klinghoffer, an American passenger, is to open June 18 in Genoa, with many of the defendants being tried in absentia, among them Abbas, who was last reported in Algiers.

Besides laying out the case against Abbas, the prosecution report specifically absolves the Syrian government and Palestine Liberation Organization leader Yasser Arafat of complicity in the hijacking, despite indications at the time that both might have been involved. This was based on the fact that the terrorists tried to bring the ship to a Syrian port and that the organization that Abbas heads, the Palestine Liberation Front, is a member of the Arafat wing of the PLO.

The report also avoids criticizing the government of Italian Prime Minister Bettino Craxi for allowing Abbas to leave Italy last October after an Egyptian plane carrying him, an aide, and the ship's four alleged hijackers was forced by U.S. warplanes to land at a NATO base on Sicily.

While noting that there were obvious "political reasons" for Abbas to have been allowed to leave Italy, the report said that at the time he was released, ostensibly because he claimed to have negotiated the end of the hijacking in the name of Arafat, there were still no indictments irrefutably implicating him in the affair.

The case detailed in the report is based on an investigation by Genoa prosecutors Francesco Meloni and Luigi Carli and comes from confessions of at least two of the alleged hijackers, the interrogations of the other two, the testimony of dozens of witnesses among the ship's passengers and crew, and secret reports and communications intercepts provided by intelligence services of the United States, Italy and Israel.

It says that from the beginning, the Achille Lauro hijacking was planned by Abbas to have a "political propaganda" effect that would not only enhance his own standing in the Arab world but also challenge that of Arafat, who, in recent years, had been advocating a political, rather than military, solution to the Palestinian problem.

The charges against Abbas, the report states, "are many, unequivocal and overwhelming."

"In effect," the report states, "Abbas conceived the action, selected its actors, trained them for the specific enterprise, financed them, had them conducted to Italy, provided them with the means [arms] to conduct the action, intervened during the hijack giving orders making them return the ship to Port Said, rescued the members of the commando [from the ship] and tried to lead them, unpunished, to their base of departure."

Besides establishing what they say is Abbas' role at every stage of the organization of the hijacking, the prosecutors say that the hijackers have confessed to being trained at one of his camps in Algeria.

They also say that the alleged leader of the hijackers, Majed Molqi, 23, a Jordanian-born Palestinian, personally met with Abbas at Abbas' home in Tunisia to receive final orders before heading to Genoa to board the Achille Lauro with arms -- four Kalashnikov assault rifles and eight hand grenades -- sent there by other PLF officials, including a cousin of Abbas, Abbas Mohammed Issa, who is in Italian custody.

According to the Italian prosecutors, the intent of the operation, from the beginning, was to hold the ship's passengers, after the ship had been brought to the Syrian port of Tartous, as the ransom for 50 Palestinians held by Israel.

The plan failed, the investigators said, when Syrian authorities refused to cooperate and turned the ship away.

Forced to abandon the initial plan, the prosecutors charge, Molqi turned on Klinghoffer, who was confined to a wheelchair because of a stroke, had him wheeled to the ship's stern, then shot him twice and had his body thrown overboard with the wheelchair.

Of the 16 suspects named as having been part of the plot to hijack the Achille Lauro, only four will be in court -- three of the alleged hijackers and Mohammed Issa Abbas, who was arrested in Genoa on charges of carrying forged papers after he had allegedly brought the weapons into Italy by ferry from Tunisia just before the Achille Lauro sailed.

A fourth alleged hijacker, who was 17 at the time of the crime, has been turned over to juvenile court for a separate trial. The others are still at large.