JERUSALEM — Ailing spy Marcus Klingberg, jailed in 1983 for passing biological warfare secrets to the Eastern Bloc, will be released from prison in less than two weeks after serving 15-1/2 years of his 18-year sentence.

But Klingberg, 80, will be under stringent surveillance 24 hours a day at home and will be allowed to leave his house for only two hours each day, according to the Beersheva District Court, which ruled in favor of his release on Thursday of last week.

In handing down its ruling, the court noted that "the state must bear in mind humanitarian considerations and not merely security."

Klingberg's lawyer Avigdor Feldman, who had been fighting a legal battle for his client's release for more than three years, said, "This is an important and humane decision and I sincerely hope the state will not appeal against it."

Klingberg took his appeal to court when the Prisons Service parole board rejected his request for a one-third reduction, in February 1997.

Devora Hen, who represented the State Attorney's Office, asked for time to consider an appeal. The court complied and decided to delay the release.

Speaking after the decision, Feldman said that the Shin Bet, Israel's domestic counter-intelligence agency, no longer objected to Klingberg's release on security grounds, since the "mystical" claim that he knew something that others could extract from him had been disproved. The testimony of former Shin Bet head Ya'acov Perry had helped on this issue, and the court also considered Klingberg's serious health problems and advanced age, Feldman said.

"He will go back to anonymity and no one will be interested in Klingberg after his release," the attorney said.

An emotional Klingberg said that he thanked the court and his lawyer. "My health has deteriorated rapidly in the past two weeks. I hope I shall have the chance to be in freedom for a while," he said, adding: "No one else has ever been in jail so long for this type of thing in Israel."

Klingberg, a world-renowned epidemiologist specializing in germ warfare, disappeared under mysterious circumstances in January 1983 while on his way to a scientific convention in Europe.

At the time, he was deputy head of the biological research institute in Ness Ziona. A news blackout was imposed on his arrest and trial, and he was kept in jail under an assumed identity.

There were rumors that he had defected to Moscow.

Only 10 years later was the blackout lifted and foreign media published reports that Klingberg had handed sensitive information on biological warfare to the Soviet Union and East Germany. The information was said to have damaged not only Israeli interests, but those of the West. The reports said he had been tried and sentenced to 18 years' imprisonment.

As deputy head of the Ness Ziona institute, Klingberg frequently traveled abroad, accompanied by his wife, Wanda. They would also go to Switzerland for health treatments, the media reports said. When the scientist was arrested, Wanda, then 70, was with him and was detained on suspicion of aiding her husband. She reportedly tried to commit suicide and was rushed to Ichilov Hospital in Tel Aviv where her life was saved, the reports said. Klingberg himself reportedly tried three times to take his life.

Last week, Klingberg telephoned from the courtroom to tell his daughter Sylvia of his release and she decided on the spot to fly here from Paris, where she lives with her husband, Udi Adiv, who was convicted of spying for Syria.

Klingberg will be living under stringent conditions when released from prison. He will have caregivers approved by the Shin Bet and will be monitored 24 hours a day. The people with whom he is allowed to meet will be strictly controlled.

"He is happy to gain his freedom. We can live with that," Feldman said.