Two Israeli soldiers were killed and two wounded today in an ambush in the narrow buffer zone in southern Lebanon. The two soldiers were the first killed in the zone since the Israeli Army ostensibly completed its withdrawal from Lebanon on June 10.

The Army command in Tel Aviv said the soldiers were killed when an Israeli patrol encountered a guerrilla squad east of the village of Majdel Silim, about four miles inside Lebanon and west of the Israeli border town of Kiryat Shemona.

In an exchange of fire, three guerrillas were killed, an Army spokesman said. He said the two wounded Israeli soldiers were evacuated by helicopter to a hospital in northern Israel.

The guerrillas had in their possession Kalashnikov assault rifles, rocket-propelled grenade launchers, hand grenades and communication equipment, the spokesman said. Israeli Army and South Lebanon Army troops were reported to have conducted a house-to-house search of the area.

The Army command did not disclose to what militia or guerrilla organization the attackers belonged, or how many participated in the attack, but the area is heavily Shiite Moslem and has seen a recent upsurge in Shiite guerrilla activity.

The guerrillas were believed to be from Amal, the Shiite Moslem militia, which frequently has attacked South Lebanon Army forces in the security zone. But it has not attacked Israeli troops and has said it does not intend to engage the Israeli Army.

The Israeli soldiers killed were a 19-year-old sergeant and a 19-year-old corporal.

Although the Army announced nearly two months ago that it had completed the final phase of its withdrawal from Lebanon -- three years after the invasion that took Israeli forces into Beirut -- the government's publicly stated policy has been to authorize armored patrols into the "security zone" established by the Army and controlled by the Israeli-backed South Lebanon Army and local civil guards sympathetic to Israel.

The zone, five to eight miles wide, starts at Israel's northern border and stretches from the Mediterranean Sea to the foothills of Mount Hebron to the east. While most Israeli troops are based south of the international border, Army patrols regularly are sent inside the zone to "prevent terrorist activity," according to government spokesmen.

The Army also reportedly maintains reconnaissance positions just north of the frontier for daylight observation, but does not keep a permanent presence in Lebanon, according to defense officials.

The continuing Israeli Army support of the SLA includes military liaison with its senior command, continued training and arming of its troops, and payment of wages. The SLA's strength of 1,200 regulars has been partly depleted by defections of its Shiite Moslem minority to Shiite guerrillas north of the zone,

Despite the imposition of strict security regulations -- vehicles must have a minimum of two occupants to discourage suicide car bombings and walking outside villages after dark is prohibited -- Israeli and South Lebanon Army troops have regularly come under attack by Lebanese guerrillas.

On July 31, two Israeli soldiers were wounded when a car bomb detonated as an Israeli patrol approached it near the village of Arnoun. The driver was killed.

[News agencies have reported from Lebanon that witnesses said three Israeli soldiers were killed in the July 31 attack, but the Israeli Army denied the reports.]

It was the fourth such suicide bombing in the last month directed at Israeli troops in southern Lebanon, and was followed two days later by Israeli Air Force strikes against a headquarters in the Bekaa Valley of the Lebanon-based Syrian National Socialist Party.

The Army command then linked the air strike directly to the car bombing, once again establishing the open policy of retaliatory air raids.

Deputy Prime Minister David Levy, who was visiting the Israeli border town of Shlomi nearby, hinted at a reprisal attack in an interview on state radio tonight.

"We have the ability to strike at the terrorists and to prevent their activities . . . . There are places where the local population knows perfectly well what it can expect. Israel will take all the measures that will insure that there will be no danger on our border," Levy said.