100,000 Lebanese Flee as Israel Steps Up Assault : Mideast: Toll mounts on 3rd day of campaign to rout guerrillas. Rocket attacks on northern Israel diminish.

More than 100,000 Lebanese fled their villages Tuesday as Israeli warplanes and artillery intensified the bombardment of southern Lebanon on the third day of a campaign against pro-Iranian guerrillas.

Residents of 70 farming villages and market towns adjacent to Israel’s self-proclaimed “security zone” in southern Lebanon were forced from their homes as Israel stepped up its offensive to deny Hezbollah militia any ability to operate in the region.

Many of the villages were reduced to rubble as Israeli fighter-bombers and helicopter gunships carried out 300 missions in the region Tuesday and Israel’s heavy guns fired thousands of rounds of high explosives.

By nightfall, smoke was rising from virtually every hilltop in the area, according to journalists there, and pine woods were burning brightly after repeated air strikes.

Lebanese authorities said that 19 civilians and guerrillas were killed and more than 150 others wounded Tuesday. Twenty more people were believed killed when a village bomb shelter collapsed on them and rescuers were unable to reach them because of the continuing Israeli attacks, according to a U.N. official.

In Israel, two people were lightly wounded by shrapnel from rockets fired by Hezbollah from across the border, according to military spokesmen. After heavy barrages of more than 100 rockets Sunday and Monday, only a dozen or so hit northern Israel on Tuesday.

Roads out of the region were choked with residents trying to escape in cars, buses and trucks, according to journalists in southern Lebanon. Some people rode in farm wagons pulled by tractors; others placed what possessions they could on mule carts and walked beside them.

With more than a quarter of a million people living in the region, Israeli military intelligence estimated that more than 100,000 had fled by Tuesday afternoon. U.N. officials in Beirut put the number of refugees at 120,000.

As most headed north to the relative safety of Beirut, Israeli Prime Minister Yitzhak Rabin said his government’s intention was, in part, to create “a mass flight” out of the region, causing a civil crisis in Lebanon that would force President Elias Hrawi to disarm and disperse Hezbollah, or Party of God.

Rabin, speaking to Israeli lawmakers and later to his field commanders, reiterated his determination to drive Hezbollah from southern Lebanon so that Israel’s northern communities, its forces in the border region and the Arab-Israeli peace talks can no longer be held “hostage” by the guerrillas.

Israel hopes to wind up the operation within a few days, Rabin said. He added that there is no intent to carry it on for even another week, and no plan to commit ground troops.

Fears were spreading, however, that the Israeli operation had already jeopardized the Arab-Israeli negotiations and that, unless brought quickly to a conclusion, it could grow and involve Syria, one of Hezbollah’s patrons.

President Clinton summoned Secretary of State Warren Christopher back to Washington from Singapore on Tuesday to discuss the violence, the worst Arab-Israeli conflict since Israel invaded Lebanon in 1982.

Christopher is expected to visit the region as planned next week. But Israeli diplomats acknowledged that most of his efforts will now be directed at halting the fighting rather than moving Israeli-Palestinian and Israeli-Syrian negotiations ahead.

Syria, in a stiff warning to Israel, said that continued Israeli attacks would “pose a serious threat to the Middle East peace process.” Syrian state radio, meanwhile, charged Israel with deliberately attacking Syrian forces--six soldiers were killed Sunday--and said it was risking a wider war.

But Uri Savir, director general of the Israeli Foreign Ministry, said there was “no reason for a Syrian-Israeli confrontation” over the operation in Lebanon. “Strategically, I would see identical interests if Syria is really interested in the peace process,” Savir said. He asserted that Hezbollah’s escalating attacks had already undermined the negotiations badly.

The raids began Sunday as a retaliatory strike following Israel’s loss of seven soldiers to Hezbollah attacks this month. But they assumed a dramatically different character Tuesday with the massive bombardment, the wholesale flight from the region and the threat to the Hrawi government.

“The one who is paying the full price, the heaviest price, is Lebanon,” Israeli Foreign Minister Shimon Peres said during a visit to northern Israel. “Hezbollah hurts us, but it hurts Lebanon more deeply.”

The intensity of the Israeli attack could be seen at Nabatiyeh, a market and crossroads town of 35,000, which Israeli artillery hit with 1,000 rounds over a period of 10 hours--more than one shell a minute, according to Israeli commanders.

Such Hezbollah strongholds as Jibsheet were also hit hard, as were Palestinian refugee camps near the cities of Sidon and Tyre. Maj. Gen. Herzl Badinger, the Israeli air force commander, said 150 targets had been hit by fighter-bombers and helicopter gunships during the day.

Residents in the targeted villages and towns had been told in radio broadcasts and leaflet drops to leave, according to Israeli military sources. Where they had been slow to go, Israeli forces fired flares and smoke rounds to drive them away.

In a new warning Tuesday night, the radio station of the South Lebanon Army, an Israeli-recruited militia, said Israeli helicopters would attack any cars on the road north of the security zone.

The military effect of the operation will thus be an extension, and in some places a virtual doubling, of the buffer along Lebanon’s border with Israel. It will establish the territory, cleared of villagers, as a virtual free-fire area.

But the price appears to have been the methodical destruction, as well as the depopulation, of many of the communities of southern Lebanon.

While declining to give the precise dimensions of the area attacked on Tuesday, Israeli officials said their aircraft were hitting “Hezbollah posts and other terrorist organizations next to and within villages and towns throughout the sector north of the security zone.”

Israeli commanders acknowledged that there had been civilian casualties, and Badinger said that Israeli planes Tuesday had mistakenly bombed a U.N. outpost, wounding three Nepalese soldiers stationed there on a peacekeeping mission.

More than 100,000 Israelis, warned by the army that there would be further attacks, remained underground in bomb shelters. But many people, growing tired of the difficult conditions in the shelters, left for central Israel.

“This is worrisome,” said Ariel Sharon, the former defense minister and general, on a visit to the Israeli north. “These are the places where people should stay. They are needed. It is the front line for all of us.”