Israeli warplanes bombed and rocketed a Syrian-backed guerrilla base in Lebanon's Bekaa Valley today in retaliation for a series of recent suicide car bombings in or near the narrow security zone that the Israeli Army established when it withdrew most of its troops from southern Lebanon.

The Army command in Tel Aviv characterized the air strike as a reprisal, signaling what could be a return to a policy of openly linking bombing raids in Lebanon to specific terror attacks against Israeli troops or Lebanese civilian targets there.

A spokesman for the Israel Defense Forces said tonight that today's sorties were against a headquarters of the Lebanon-based Syrian National Socialist Party, which has claimed responsibility for at least four car bombings during the past month directed at Israeli troops in southern Lebanon or members of the Israeli-backed South Lebanon Army.

News agency reports from Shtawrah, where today's air raid occurred, said that a party headquarters building was damaged heavily, and that at least two members of the organization were killed. Beirut radio stations reported far heavier casualties.

In the most recent incident in southern Lebanon, on Wednesday, a Lebanese civilian was killed and two Israeli soldiers wounded when a suicide car bomber detonated his vehicle near the village of Arnoun, at the northern edge of the security zone controlled by the SLA.

A Lebanese teen-ager who detonated the car as an Israeli Army patrol approached -- and died in the explosion -- was reported to have identified himself as a member of the Syrian National Socialist Party in a videotaped interview before the mission.

That attack was the first directed against Israeli forces inside the SLA-controlled zone in recent weeks, but there have been similar suicide bombings on or close to the line behind which Israeli forces have withdrawn.

Israeli troops ostensibly have withdrawn completely from Lebanon, but military officials acknowledge that armored patrols are routinely mounted by the Army to "prevent terrorist acts."

The Syrian National Socialist Party is a Lebanese political party that advocates the creation of a "Greater Syria" encompassing Syria, Lebanon, Israel, Jordan, Iraq and Kuwait. The group's leader, Issam Makhiri, is reported by Israeli intelligence sources to take orders directly from Syrian President Hafez Assad.

While Israeli Air Force jets have launched several air strikes in the Bekaa during the past two weeks, today's raid was the first attributed directly by the military command to a renewed reprisal policy and openly declared as retaliation for a specific guerrilla operation in southern Lebanon.

On Monday, Israeli jets bombed a Palestinian guerrilla base controlled by Ahmed Jibril, head of the Popular Front for the Liberation of Palestine, in the Syrian-controlled Bekaa Valley.

However, the Israeli military command said that the air raid was not a retaliatory strike, but part of the ongoing Israeli policy of "striking anywhere, anytime" to counter threats of terrorism against security forces in Lebanon or civilians in Israel.

The retaliatory nature of today's air strike recalled a policy openly declared for the first time a year before the 1982 invasion of Lebanon, when the government of then-prime minister Menachem Begin announced that its frequent air raids in Lebanon against PLO positions were not necessarily preventative measures, but were reprisals for specific terrorist operations.

That shift of publicly stated policy heralded a period of cyclical terror attacks and answering air strikes that lasted until the June 6, 1982, Israeli invasion of Lebanon.

Israeli military and political sources have gone to some lengths during the past week to stress that a recent spate of kidnapings and killings of Israelis in the occupied West Bank and in areas inside Israel close to the pre-1967 demarcation line were not connected to organized Palestinian guerrilla groups operating either in Lebanon or Jordan, and that retaliatory air raids were not anticipated.

The officials include Defense Minister Yitzhak Rabin and Minister of Police Haim Bar-Lev, both of whom have said that the new wave of attacks on Israelis appeared to have been committed by Palestinian nationalists operating independently of any organized liberation groups and who were motivated by rising tensions between Palestinians and Jewish settlers in the West Bank.

Meanwhile, the West Bank military command announced today that it had closed the An Najah University in Nablus, the largest Palestinian university in the West Bank, after the slaying earlier this week in Nablus of an Israeli civilian.

Following the killing, security forces raided the An Najah campus and, according to a military spokesman, found evidence that several Palestinian nationalist groups had been holding meetings there. An Army command spokesman said tonight that security forces also confiscated inflammatory literature from university buildings.