Israeli warplanes, streaking in pairs out of a low haze over the Mediterranean, repeatedly bombed and rocketed Palestinian positions along these coastal hills south of Beirut today.

Two Syrian Migs that rose to meet the attack were shot down by other Israeli jets.

The Israeli assault followed by only hours the killing of an Israeli soldier and the wounding of a second in southern Lebanon by a land mine that Israeli officials charged was planted by Palestinian guerrillas. The men were in the part of Lebanon controlled by Israeli-backed Christian militias.

The air raids, which lasted two hours, marked the first clash between Israel and the Palestine Liberation Organization in Lebanon since a cease-fire was worked out under U.S. patronage last July. They raised the specter of retaliation by PLO artillery in southern Lebanon and still more devastating strikes by the militarily superior Israeli forces.

A spokesman for Israeli Prime Minister Menachem Begin said the raids were meant as a warning to the PLO to stop what he described as violations of the nine-month cease-fire, The Associated Press reported. The spokesman, Uri Porat, said: "If the PLO learns the lesson from today's attack, from our point of view the cease-fire can continue. This was a reminder to those who forget that violations of the cease-fire cannot be one-sided."

The Palestinian guerrilla leader, Yasser Arafat, presided over an emergency session of his military command tonight and a spokesman declared, "We know how and when to respond." Arafat also addressed a complaint to U.N. Secretary General Javier Perez de Cuellar, accusing Israel of attacking populated Lebanese areas in violation of the nine-month-old cease-fire. He stopped short of declaring it void, however.

The Security Council is to meet at 11 a.m. Thursday at Lebanon's request to consider sanctions against Israel because of the raid, United Press International reported.

Lebanese security officials said preliminary estimates showed 23 persons were killed and several dozen wounded in the three separate waves of Israeli attacks. Ambulances, some escorted by jeeps mounted with 106 mm recoilless rifles, raced up and down the coastal highway, their sirens wailing, as Israeli jets roared overhead and Palestinian antiaircraft fire rattled into the sky.

The delta-winged Israeli warplanes sped in from over the sea, coming out of the afternoon sun to make sighting difficult for antiaircraft gunners manning Soviet-designed ZSU23 batteries mounted on trucks. As the antiaircraft guns in this coastal town fired thousands of rounds into the clouds, the Israeli jets approached in two-plane teams, then peeled into separate dives toward their targets while releasing decoy balloons to deflect the PLO's heat-seeking SA7 antiaircraft missiles.

The first sign of an Israeli bomb hitting the ground was a brilliant ball of flame on the rocky hillsides that rise from the coast here. Almost instantaneously the flames were surrounded by heavy smoke that billowed slowly into the air. There was a pause and then the ground shook and the sound of the explosion thudded out to sea.

In raids that began about 2:30 p.m. and lasted until 4:30, the Israeli planes hit targets in Damour, Naameh, Aramoun, Saadiyat and the exclusive hilltop suburb of Doha, the site of some Syrian radar units, according to Palestinian and Lebanese officials. In separate announcements, the PLO and the Israeli military said the raids also hit Palestinian positions near Sidon, but Lebanese journalists in that port city 25 miles south of Beirut said the Israeli planes criss-crossed the region without bombing it.

About midway through the assault, Syria sent planes to challenge the attacking Israeli craft. Syria announced two of its planes were shot down, without specifying the type, and claimed it downed one Israeli plane. Israel said the two downed Syrian planes were Soviet-made Mig23s and insisted all its aircraft returned safely to their bases.

Israel has now claimed to have shot down 15 Syrian planes and lost none since President Hafez Assad's government sent peace-keeping forces into Lebanon in 1976 and began protecting Lebanese air space from Israeli attack. Although Assad's Air Force has the latest Soviet equipment, including Mig25s, the electronic gear in Israel's U.S.-made F15s has given it what appears to be clear superiority in the air judging from the outcome of combat over Lebanon.

A radio station run by Lebanon's Christian Phalange Party reported Syrian SA6 missiles were fired at Israeli planes over eastern Lebanon's Bekaa Valley and that Israeli planes sought to destroy the batteries. Lebanese government officials discounted these reports, however, and neither Syria nor Israel said anything about the much-disputed SA6 sites.

A PLO communique said about 60 Israeli planes participated in the attack, describing them as F15s and F16s. About a dozen planes were seen during the raids. Viewed from a distance, they appeared to be F4 Phantoms or Israel's home-built Kfirs, with their distinctive delta shape.

Other Israeli planes flew back and forth across Beirut at the same time, drawing antiaircraft fire that echoed up and down the city's narrow streets. There were no reports of any bombing of Beirut itself. An Israeli air raid on PLO offices in a downtown Beirut neighborhood last June killed as many as 300 people, most of them civilians, according to a Lebanese government count.

The targets south of Beirut, as far as could be determined by driving up and down the area, were offices and military positions of PLO guerrillas and their allies in Lebanese leftist militias and the breakway Lebanese Arab Army allied with Fatah, the main PLO group.

A PLO communique charged, however, that one rocket made a direct hit on a Palestinian orphanage school at Ein Masdoud in the hills behind Damour. A string of bombs that landed in Doha, also on a ridge above Damour, appeared to have wreaked destruction among a group of luxurious villas. PLO guards prevented foreign correspondents from approaching the houses.

Similarly, guerrillas refused to allow reporters to enter another bombed-out building flush on the sea next to a former resort called Family Beach. The low, concrete building was said by Lebanese sources to contain PLO boats.

"You can say it is a little PLO office," said a Fatah officer who warned away journalists, saying another bombing run was possible.

An Israeli communique described the targets as bases for terrorist raids and ammunition stores.

Lebanese sources linked the raid to the controversy over Israel's withdrawal in the Sinai, claiming Prime Minister Menachem Begin decided on the attack as a gesture to public opinion in Israel upset over the prospect of violence by the Israeli Army against extremists who refuse to leave by the Sunday deadline.

The attack appeared to have little effect on the PLO's military might, which Israel has charged is concentrated in southern Lebanon.

Special correspondent Yuval Elizur filed this report from Jerusalem:

Lt. Gen. Rafael Eitan, chief of staff of the Israeli Army, expressed the hope that the attacks would not bring an end to the nine-month-old cease-fire between Israel and the Palestine Liberation Organization.

"What will happen now will depend on the PLO. If they maintain the peace, we shall certainly do likewise," Eitan told a press conference.

Other Israeli officials, although expressing similar hopes, said that what happens next will depend not only on the PLO but also on Syria.

Asserting that the PLO has committed 32 violations of the truce since last July, Eitan said, "We decided to put an end to this one-sided game," He said the violations, even though they occurred in Western Europe or were carried out across the Jordan River or inside the occupied territories, actually originated in Lebanon.

Although as of this evening the situation remained quiet along the border between Israel and Lebanon, the Israeli settlers in the region were preparing for possible PLO retaliation. Police cars equipped with loudspeakers drove through the streets of Kiryat Shmona alerting the population, suggesting that the air raid shelters be made ready.

Israeli officials briefed the United States and Egypt on the aims of today's raid. Defense Minister Ariel Sharon met with Undersecretary of State Walter Stoessel as soon as the planes completed their mission.

According to reliable sources here, while the targets were carefully chosen in advance and even the decision to try to limit the scope of the raid had already been made some time ago, the final decision to send the planes may have come only today.

During this morning's Cabinet meeting, which affirmed the decision to complete the withdrawal from Sinai next Sunday, Prime Minister Begin received a message that an Israeli Army lieutenant had been killed when his vehicle hit a mine in Taibe in southern Lebanon. This incident, as well as the shooting of missiles at Israeli planes over Lebanon and the Golan Heights Tuesday, may have led to the decision to send the planes today.

Israeli government sources tonight vehemently denied the suggestion that today's raid was a "diversionary action" to draw the attention of Israelis away from the evacuation and destruction of the Israeli settler town of Yamit in the Sinai.