Several of his associates were also detained during raids at several sites around Baghdad, defense officials said. Commandos, tipped off by U.S. intelligence to Abbas' whereabouts, also seized documents and weapons.

The man known as Abul Abbas, whose name actually is Mohammed Abbas, led a faction of the Palestine Liberation Front, a Palestinian splinter group.

His faction operated out of Tunisia until the October 1985 attack on the Achille Lauro, after which it relocated to Iraq. His group was also responsible for some attacks in Israel.

"He got away from us, and we've been chasing him ever since," said Vince Cannistraro, a former CIA counterterrorism chief. "He's a big catch for us. It's an old score to settle."

Abbas, either 61 or 62, had eluded arrest since his four of his followers hijacked the Achille Lauro as it sailed from Egypt to Israel in October 1985. They demanded that Israel release 50 imprisoned Palestinians.

During the hijacking, his followers shot and killed Jewish American passenger Leon Klinghoffer, 69. The hijackers then tossed Klinghoffer and his wheelchair off the cruise ship.

Klinghoffer and his wife, Marilyn, along with nine friends from the New York area, took the cruise to celebrate their 36th wedding anniversary. They were among 500 passengers taken hostage. Klinghoffer's wife died of cancer just four months after the hijacking.

The hijacking ended Oct. 9 after Egypt negotiated with the hijackers. Abbas, who helped negotiate the surrender, and the four hijackers were flown out of Egypt on a jet that was intercepted by U.S. Navy fighters and forced to land in Sicily.

Tensions arose as soon as the plane landed. Armed U.S. and Italian soldiers faced off, each side demanding custody of the hijackers. The situation was only resolved after feverish telephone calls between Premier Bettino Craxi and President Reagan.

During the affair, Reagan told reporters, "Terrorists everywhere - you can run but you can't hide."

The Italians took custody of the four and promised to try them, but refused to detain Abbas, saying the evidence compiled by Washington was insufficient and that he held an Iraqi diplomatic passport. Within two days, he slipped out of the country.

Two weeks later, Italian magistrates filed charges against Abbas and issued an arrest warrant, which has remained outstanding.

In June 1986 he was tried in absentia, convicted and sentenced to life imprisonment for masterminding the hijacking. The sentence was upheld on appeal.

Ten years later, Abbas apologized for the slaying.

"The killing of the passenger was a mistake. ... We are sorry," he said.

Abbas was a member of the Palestine Liberation Organization's executive committee from 1984 but left in 1991, according to the U.S. State Department.

In 1994, the Achille Lauro caught fire in the Indian Ocean off Somalia and sank.

The U.S. Justice Department has said it has no grounds to seek Abbas' extradition, as there is no outstanding warrant against him. The American warrants were dropped after his conviction in Italy.

A so-called "long-arm" U.S. statute, to aid in prosecution of those committing terrorism against American citizens overseas, was not enacted until after the Achille Lauro hijacking.

In the 1990s, Baghdad, largely out of reach to western security services, had become home to both Abbas and Abu Nidal, another once-feared terrorist mastermind.

Last year, Abu Nidal died violently in Baghdad. Iraqi officials said he committed suicide; Abu Nidal's supporters say the Iraqis killed him.

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