Israeli warplanes, hoping to capture Palestinian terrorist leaders, intercepted a Libyan executive jet in international air space near Cyprus today and forced it to land at a military air base in northern Israel. But Israeli officials did not find the wanted men on board.

The Israeli military command said it acted because the Libyan jet "was suspected to be carrying persons who were involved in planning attacks against Israel." It did not identify those actually on board but said all had been freed. Other reports said the nine passengers were all members of a Syrian political delegation.

The passengers and three-man crew were interrogated for five hours and then were allowed to continue their flight to Damascus, Israeli military officials said.

Libya's state-run radio said Abdullah Ahmar, assistant secretary general of Syria's ruling Baath Socialist Party, was among the passengers, but it did not identify the others.

Syria and other Arab countries condemned the interception. Syria, threatening to retaliate, called Israel's action "air piracy" and a threat to civil aviation.

Tonight, the U.N. Security Council held an emergency meeting on a request by Syria but took no action.

Syria's official news agency quoted Gen. Hekmat Chahabi, Syria's military chief of staff, as saying, "We will answer this crime by teaching those who committed it a lesson they will not forget. We will choose the time and the place," The Associated Press reported.

Syrian Vice President Abdul Halim Khaddam was quoted as saying: "We cannot let this aggression pass without letting the aggressor get the proper answer."

Jordanian television said King Hussein, in a telephone call to Syrian President Hafez Assad, had "denounced and condemned the Israeli aggression" and pledged his country's support for diplomatic efforts to censure Israel.

Arab League Secretary General Chadli Klibi called the interception an "act of piracy" and Egyptian Foreign Minister Esmat Abdel-Meguid said that "Egypt disapproves interception of civilian planes."

In New York, U.N. spokesman Francois Giuliani said Secretary General Javier Perez de Cuellar was "taking this matter up urgently with the Israeli authorities. He is deeply concerned at what appears to be a serious infringement of freedom of civil aviation and an act that could aggravate the already tense situation in the area."

In Washington, U.S. officials denied Libyan charges that U.S. naval forces in the Mediterranean had helped direct the interception.

Tripoli Radio quoted Libya's official JANA news agency as charging that "vessels of the U.S. Navy, which had been maneuvering off the Libyan coast, provided the information about the Libyan plane to the air pirates."

Pentagon spokesman Robert Sims said, "There was no U.S. military involvement at all." A State Department official added that Libyan charges of U.S. assistance to the Israelis are "a crock." He added, "We had no foreknowledge or involvement in any shape or form."

In a later statement, State Department spokesman Bernard Kalb said that "as a matter of general principle, the United States opposes the interception of aircraft in a peacetime situation," but that "in certain very narrow counterterrorism cases, such measures can be justified."

The U.S. statement added that "we believe that states should intercept an aircraft only on the basis of the strongest and clearest evidence that terrorists are on board," and Kalb said that Israel had "made its own decision on the basis of its own evidence."

Officials here refused to say who they thought was aboard the Libyan jet, but the target was rumored to be Abu Nidal, head of a group accused in the Dec. 27 terrorist attacks at the Rome and Vienna airports in which 20 persons, including five Americans and four terrorists died.

Both the United States and Israel have accused Libyan leader Muammar Qaddafi of involvement in the airport attacks.

Qaddafi chaired a weekend meeting in Tripoli of 22 hard-line Palestinian and other Arab groups to plan a response to U.S. economic sanctions imposed against Libya following the December attacks.

Those who attended the meeting agreed to form a suicide force to strike at American targets worldwide if the United States attacked Libya or any other Arab nation, AP reported. It said Abu Nidal was not seen at the meeting, but George Habash, head of the Marxist Popular Front for the Liberation of Palestine and the target of an earlier Israeli interception, was present.

In 1973, Israeli jets forced an Iraq Airways passenger plane to land here, but Habash had changed his flight plans at the last minute.

Israeli officials insisted that today's action was justified, given the threat of international terrorism.

Foreign Minister Yitzhak Shamir called Libya "a center of international terrorism whose government assists the terrorist organizations to perpetrate terrorist acts against Israel" and said that "Israel has the right to take measures in order to prevent acts of murder and sabotage."

A spokesman in the office of Prime Minister Shimon Peres said: "The suspicion was the terrorists were on board, and in such a case it's legitimate. I mean, Libya is not exactly the country that is above suspicion."

First word of the incident came about 1 p.m. today (6 a.m. EST), when the pilot of the Libyan executive jet, reportedly a Grumman Gulfstream II, radioed air traffic control in Cyprus to say that he had been intercepted by two jets rocking their wings in the internationally accepted signal to "follow me."

The Cyprus tower then lost contact with the jet and at one point launched an air-sea search operation in the belief that it might have ditched in the sea, the British Broadcasting Corp. reported.

The Israeli military command said later that the Libyan pilot "obeyed the order" to follow the fighters without any warning shots being fired. The plane landed at a military airfield.

Israeli censorship forbade any reports on the incident from here for nearly three more hours, at which time an official statement declared that "the passengers and crew are being treated well."

The plane took off again for Damascus about five hours after it landed here, according to an Israeli military spokesman. Sources at Damascus airport said it landed about 90 minutes later.