Fawaz Younis, the accused Shiite Moslem hijacker arrested at sea by FBI agents, was apparently set up by a longtime friend and lured aboard a rented yacht with the promise of a drug deal and a shipboard party, according to informed sources.

The undercover operation last Sunday was the first arrest abroad by U.S. law enforcement officials of a suspected terrorist being sought under U.S. laws. It was denounced yesterday by Lebanon justice minister Nabih Berri, leader of the Shiite Moslem Amal movement, as "an attack against the honor of Lebanon."

During a news conference at his West Beirut home with other senior Amal officials, Berri called the incident "close to piracy in nature," Washington Post special correspondent Nora Boustany reported.

Berri said he had asked for a thorough investigation and indicated that he would take the steps necessary to "defend a Lebanese citizen in the first instance."

Younis, 28, is the alleged mastermind of the 1985 hijacking of a Jordanian airliner at the Beirut airport with two U.S. citizens and two U.S. "nationals" aboard. He was flown to the United States Thursday to stand trial for hostage-taking under 1984 legislation asserting "long arm" jurisdiction for terrorist activities involving American hostages.

U.S. officials remained guarded about the circumstances of Younis' arrest, but sources said yesterday that it began when Younis and a longtime friend left Beirut for a "holiday" in Cyprus.

"Once on Cyprus, the friend said, 'Let's go for a ride,' " one source recounted. "They get in a small launch, take it out to this yacht, and as soon as he walks on, bump, he's arrested."

FBI agents, male and female, were piloting the yacht, according to senior Justice Department officials. The identity of the craft remained secret, but one source speculated that it may have been "rented" from the Drug Enforcement Administration, which has offices on Cyprus.

Shiite sources in Beirut say that Younis, who is Lebanese, has been involved in drug trafficking and smuggling and that he was expelled from the security arm of Amal earlier this year, Boustany reported. Senior Amal officials at the Berri news conference would not concede, however, that he was no longer part of the Amal movement. Justice Department officials described him as a full-time member of the Amal militia.

According to U.S. officials, he was lured by the prospect of buying drugs for resale later. Some sources said there was also talk of a party. In any case, the friend who accompanied Younis apparently dropped out of sight after Younis stepped onto the yacht, carefully positioned in international waters.

The FBI team took Younis further out in the Mediterranean where he was put aboard a U.S. Navy vessel that headed west for a rendezvous off Corsica with the U.S. aircraft carrier Saratoga. "It was several days' sail from where the pinch was made to where the Saratoga was," one official said.

The suspect was then flown to Andrews Air Force base here in a small transport jet capable of aerial refueling. The nonstop flight took about 13 hours.

"That's how we could say no other governments were involved," one official said of the midair refueling. "This was purely an American operation."

Now being held at Quantico Marine base, Younis has pleaded not guilty and is scheduled to return to the U.S. Courthouse here Tuesday for a bail hearing. His court-appointed attorney, Frank Carter, said he expects the government will seek "preventive detention."

Security at Younis' arraignment Thursday was the tightest in at least 20 years, according to courthouse veterans.

Some officials said it is ironic that Younis should be the first snared under the long-arm law. The 1985 hijacking involved an Arab versus Arab dispute and was not aimed at the few Americans who happened to be aboard. Other officials pointed out, however, that Younis was caught on videotape at a news conference making threats about the passengers and that the hijackers not only beat up Jordanian skymarshals on the plane, but blew up the craft after releasing those aboard.

Staff writer Nancy Lewis contributed to this report.