srael said that its attacks on Palestinian and Syrian positions across Lebanon today were intended as retaliation for "constant violations" of the cease-fire culminating in the death of five Israeli soldiers in an ambush Wednesday.

Government sources said the renewed Israeli air attacks were meant to be a "limited action" aimed at putting the Palestine Liberation Organization and especially Syria on notice that Israel will not stand for a war of attrition.

"Israel has no intention of renewing the war against Syria but, on the contrary, of bringing about a situation where there is a complete cease-fire," they said.

Ever since June 11, when the first cease-fire came into effect, the sources asserted, the Syrians had "continuously" violated it by improving their positions, trying to bring antiaircraft missiles into the Bekaa Valley and helping PLO guerrillas infiltrate Israeli lines to lay mines, sabotage and attack Israeli positions.

The high point of these violations had come early Wednesday when Palestinian guerrillas ambushed an Israeli patrol east of Lake Qirawn in the southern Bekaa and killed five Israeli soldiers, the sources said.

Why Israel had decided to bomb Palestinian camps and military targets in West Beirut was less clear, but one government statement said the guerrillas trapped there had also violated the cease-fire repeatedly.

The sharp escalation in fighting came after Israeli officials reported there had been "no progress" in the stalled negotiations over the withdrawal of the guerrillas from the city. Contrary to reports coming from Washington Tuesday, there had been "no new ideas" proposed to break the impasse, the government sources said.

For weeks now, Israel has been warning that it will launch a full-scale assault on West Beirut once it is convinced the talks have reached a dead end. Today's air attack on West Beirut appeared designed to reinforce that warning.

Officials here went to great lengths today to stress that Israel would continue to pursue a peaceful settlement "until all diplomatic efforts have been exhausted." They made it clear nonetheless that the government was "very skeptical" anything was being accomplished any longer by U.S. negotiator Philip C. Habib, who left Beirut for Damascus and talks with Syrian leaders.

This latest Israeli assessment came after U.S. Ambassador Samuel Lewis had briefed Prime Minister Menachem Begin on the results of President Reagan's meeting with the Syrian and Saudi foreign ministers in Washington Tuesday.

"No new ideas were presented to us to change the two main issues which we are focusing on," Israeli officials said, referring to a definite Palestinian commitment to leave West Beirut and to a new location outside Lebanon for the guerrillas.

Today's military action began at 4:30 p.m. local time when Israeli warplanes, tanks and heavy artillery opened fire on Syrian and Palestinian positions "all along the cease-fire line" in the Bekaa Valley, a military communique said.

A later communique, however, said that a Syrian armor and military concentration was hit at Baalbek, which is far north of this line in the upper Bekaa Valley.

At 5 p.m., the military said, the Israeli air attack began on Palestinian camps and military targets on the southern edges of West Beirut.

Israeli forces had stopped their attack as of 6 p.m. and all warplanes had returned to their bases safely, the military said, declaring that Israel would again respect a cease-fire.

It was the first time since June 25, when the second of six cease-fires went into effect, that the Israeli Air Force had been used against either Palestinian or Syrian positions in Lebanon.

Both government and Army spokesmen made it clear that the air attacks were aimed primarily at Syria, which they accused of acting in collaboration with the Palestinian guerrillas and allowing them to infiltrate Israeli lines in the Bekaa. Israeli radio, quoting military sources, said that since the first cease-fire went into effect June 11, there had been 75 incidents involving Palestinians operating out of Syrian-controlled territory in the Bekaa.

The initial Army communique issued at 5 p.m. made no mention of the bombing of Beirut and gave as a rationale for the Israeli action only the alleged Syrian and Palestinian violations in the Bekaa.

Later, in an interview with Israeli radio, Deputy Foreign Minister Yehuda Ben Meir said: "Anyone who knows Israel realizes that we are not going to stand idly by while our soldiers are killed and while the Syrians and the terrorists who are acting with the permission of the Syrians and the support of the Syrians, from areas controlled by the Syrians, . . . put ambushes and attack and kill our soldiers.

"There cannot be a unilateral cease-fire. Syria is responsible for any attacks against our soldiers," he asserted. "She will bear the full responsibility for the consequences."

Israel's frustrations with the situation in the Bekaa came to a head after the five soldiers were ambushed and killed near the village of Mansurah, east of Lake Qirawn. The army said four guerrillas had infiltrated from the area under Syrian control along the border and that all four had been killed after staging the ambush.

It was the latest in a spate of incidents that began several weeks ago, including a mine explosion killing six Lebanese children and wounding 24 others traveling in a truck on July 11, and the firing of a Katyusha rocket on northern Galilee Tuesday night by two guerrillas who managed to infiltrate behind Israeli lines.

The army has said that the guerrillas were infiltrating in groups of up to seven and laying mines on roads, setting up ambushes for Israeli patrols and occasionally firing on their positions.

The situation in the Bekaa Valley makes it difficult for the Israelis to control or block guerrilla infiltration. By the time the war came to a halt with a second cease-fire June 25, the Israelis had pushed most Syrian troops and armor out of the valley south of the Beirut-to-Damascus highway. But Syrian forces still remained inside Lebanon along the Syrian border south of the highway.

It is from these Syrian lines that most of the Palestinian guerrillas now are apparently infiltrating Israeli lines across the Bekaa and even into the highlands to the west.