A German judge today convicted four people of an old act of terrorism against Americans -- a 1986 bombing in Berlin that killed two American servicemen -- and ruled that the Libyan intelligence service helped plan the attack.

Ending a four-year, labyrinthine trial, Judge Peter Marhofer also ruled that charges that the Libyan leader, Moammar Gaddafi, personally ordered the bombing at the La Belle nightclub, a popular nightspot among U.S. servicemen, were not proven. The judge attributed that failure to the unwillingness of U.S. and German intelligence services to provide critical evidence that prosecutors believed to be in the agencies' possession.

But he said that "Libya bears at the very least a considerable portion of the responsibility for the attack."

The disco bombing prompted the United States to retaliate with an air raid on Libya 10 days later. Among the approximately 37 people killed in the U.S. attack was Gaddafi's 15-month-old adopted daughter. U.S. officials contend that in 1988, Libya struck out again, arranging the bombing of Pan Am Flight 103 over Lockerbie, Scotland, with the loss of 270 lives. A Scottish court convicted a Libyan of that bombing in January; another man was acquitted.

Prosecution of the disco bombing case had floundered until the fall of the Berlin Wall, when documents from the Stasi, the East German secret police, as well as testimony from Stasi agents, helped lead investigators to the defendants.

Today's verdict, which fell short of fingering Gaddafi himself, comes as the German government seeks to improve relations with Libya. Gaddafi's son, Saif Islam, visited Berlin last week and offered to mediate with the Taliban in Afghanistan to help free imprisoned Western aid workers.

Gaddafi's son also said Libya would not pay compensation to the victims of the La Belle bombing, the German press reported. And Libya has refused to extradite five other suspects, including members of its secret services, sought by German investigators.

Earlier this year, Chancellor Gerhard Schroeder's foreign policy adviser, Michael Steiner, was reported to have told President Bush that Gaddafi had acknowledged to Steiner a Libyan role in the bombings. According to leaked notes of the meeting, Steiner said that the leader had "admitted Libya took part in terrorist actions (La Belle, Lockerbie). He clarified that he had abandoned terrorism."

Prosecutors tried to summon Steiner to testify but the German government, citing national security concerns, successfully fought the motion.

The judge today found Verena Chanaa, a 42-year-old German, guilty of murder after finding that she picked the target and planted the 4.4-pound bomb in the crowded nightclub on April 5, 1986. Chanaa was sentenced to 14 years in prison.

On the night of the bombing, Chanaa was accompanied into the club by her sister, Andrea Haeusler, 36. The sister was acquitted for lack of proof that she knew there was a bomb in Chanaa's bag, the judge said.

Yassir Chraidi, a 42-year-old Palestinian who worked at the Libyan Embassy, was accused of being the main organizer. He was convicted of multiple counts of attempted murder and sentenced to 14 years.

Two other embassy employees were also convicted of attempted murder and sentenced to 12 years in prison each. They were Musbah Abdulghasem Eter, a 44-year-old Libyan, and a Lebanese-born German, Ali Chanaa, 42, Verena Chanaa's former husband.

The German indictment alleged that the bombing was revenge for a U.S.-Libya naval clash in the Mediterranean in which two Libyan boats sank.

Sgt. Kenneth T. Ford, 21, and Nermin Hannay, a 29-year-old Turkish woman, were killed immediately in the explosion. Another U.S. soldier, Sgt. James E. Goins, 25, died later of his injuries.

A number of relatives, including Goins's widow and Ford's father, were among the 150 people who packed the courtroom, where security was extremely tight. "They took my son from me and no verdict can replace that for me," said Larry Beecham, Ford's father.

And while some of the victims' family members expressed disappointment that Libya was not explicitly found guilty, lawyers for some of the American victims said the court's finding of Libyan involvement establishes a legal basis to sue the country for compensation in U.S. courts.

Among the evidence cited was an intercepted radio transmission from the Libyan capital, Tripoli, to the country's embassy in East Berlin calling for an attack "with as many victims as possible." Prosecutors also presented telegrams sent from the Libyan Embassy in East Berlin to Tripoli.

"Expect the result tomorrow morning -- it is God's will," read a telegram on April 4. The next day, another read: "At 1:30 in the morning one of the acts was carried out with success, without leaving behind a trace."

Patrocinia Goins, widow of Sgt. James E. Goins, who was killed in the bombing, and Robert Ford, father of an injured serviceman, leave courtroom in Berlin where a judge ruled that Libyan intelligence helped plan the attack.