BEIT YAHOUN, Lebanon (AP) _ South Lebanon was in chaos Monday after units of an Israeli-allied militia abandoned their positions and Shiite Muslim guerrillas _ and their supporters rushed in to reclaim villages held by Israeli forces for two decades. Six civilians were killed in the violence.

Frightened Israeli-allied militiamen surrendered en masse or sought asylum in Israel as hopes dimmed for an orderly, peaceful pullout overseen by the United Nations.

The collapse of a key section of the front line puts Shiite Muslim guerrillas on Israel's doorstep ahead of the Israeli army's self-imposed July 7 deadline.

The rapid developments _ eight villages were reclaimed by guerrillas and sympathizers on Monday and six on Sunday _ drew a warning from Israel that it could send its troops back into Lebanon to keep the guerrillas out.

Some units of the 2,500-member Israeli-backed South Lebanon Army militia were in disarray and loyal militiamen were retreating to their villages near the border to organize new defensive lines.

Early Tuesday, the Israeli army evacuated its second biggest base in south Lebanon. Convoys of trucks brought weapons, equipment and scores of soldiers across the border from the Bint Jebeil base.

Small convoys of Israeli soldiers began arriving inside Israel later as soldiers in tanks and jeeps honked horns, waved brigade banners and kissed the soil of their homeland.

``I've made it,'' one soldier shouted. Another soldier kissed the ground. One officer carried a Torah scroll.

The army described the predawn departure from the Bint Jabail as orderly.

The evacuation came after Israel's security Cabinet held a late-night emergency session, and told Prime Minister Ehud Barak he had full authority to determine the pace of the pullout, but army radio cited high-ranking army officials as saying the withdrawal would be over within a few days.

Before that meeting, Haim Ramon, a Cabinet minister and confident of Barak, said he hoped a complete pullout would come ``much earlier'' than July 7, enabling the army to engage in a broader range of reprisals.

``Up until now ... we could not react as we are capable of doing, using the full power of the (army),'' he said. ``The rules of the game are changing.''

Some in Israel painted Monday's events as an ominous takeover of the area by Hezbollah guerrillas. Israel set up the zone in 1985 to protect its border region from guerrilla attacks.

In northern Israel, the army beefed up border defenses and tens of thousands of civilians, fearing reprisal attacks, hastily gathered up children, food and schoolbooks as the army ordered them into underground bomb shelters.

Meanwhile, thousands of Lebanese converged on the reclaimed villages in Lebanon in cars, trucks and on foot, many waving flags of the Shiite guerrilla groups Hezbollah and Amal. They were showered with rice and rose petals by the few remaining villagers who emerged to welcome them.

``This is a great day and I can't express my happiness,'' said Qassem Rammal, who lived with his wife in Adaisseh, a half mile from the Israeli border.

The takeover was peaceful at first, with little resistance from the Israeli allied militiamen.

But it turned bloody when battle tanks fired artillery shells and an Israeli helicopter gunship strafed the area, apparently in an effort to scare away the approaching civilians.

It was not known immediately who or what caused the Lebanese casualties _ the tanks and howitzers on the ground, which both Israel and its militia allies have, or the gunship, which only Israel has.

The Israeli army in Jerusalem said the civilians were ``apparently killed by SLA fire.''

Israeli warplanes and artillery also attacked an abandoned SLA artillery battery to prevent it from falling into guerrilla hands, the Israeli army said. It said Israeli navy ships in the Mediterranean Sea also took part, launching missiles toward ``terrorist targets.''

Lebanese officials said two people were killed during aerial and ground firing toward crowds between the villages of Houla and Meiss el-Jabal. Two more civilians were killed by an artillery shell that hit a former SLA position in the village of Rshaf. A fifth civilian was killed by machine gun fire in the village Rob Thalatheen, and the sixth died in shelling on the village of Srobbine.

Hospital officials in Tibnine near Beit Yahoun, about 15 miles from the sea, said 19 wounded were admitted from various villages.

In Jerusalem, the Israeli army said three SLA fighters were wounded. It added a number of rockets and mortars were fired into Israel in the morning and around midday and Israeli planes and helicopters repeatedly attacked ``terrorist targets'' in south Lebanon during the day.

Monday's events began when some 500 civilians waving Hezbollah flags entered the village of Houla, about a mile from the Israeli border, witnesses said. Hundreds of others converged on Markaba, Tallousa, Rob Thalatheen, Baraachit, Bani Hayan, Adaisseh and Beit Yahoun.

When the marchers, who included bands of armed guerrillas, reached Houla, the last nine SLA militiamen in the village deserted their posts and defected to the Lebanese government, officials said. Earlier Monday, other militiamen had retreated further into the occupied zone.

Timur Goksel, spokesman for the U.N. peacekeeping force in south Lebanon, who has spent the last two decades in the region, said the SLA had ``ceased to exist as a unified force.''

In New York, U.N. Secretary-General Kofi Annan called for additional peacekeepers to be sent in to confirm Israel's withdrawal. Diplomats said, however, that with events moving so quickly, there may not be enough time.

The Israelis and their militia allies have departed from virtually all Shiite areas except Bint Jbeil, the last main Shiite town in the hands of the SLA and the Israeli army and home to 4,000 people.

That cuts Israel's so-called security zone in half, with the SLA retaining their headquarters in the Christian town of Marjayoun in the eastern sector but unable to travel to the western sector, where only a few posts adjacent to the border remain in Israeli hands, except through Israel.

SLA militiamen patrolled the streets in armored personnel carriers and set up checkpoints Monday in Marjayoun, which has a population of about 5,000.

About 100 SLA militiamen surrendered to Lebanese army checkpoints at Beit Yahoun on Monday, Lebanese officials said. They were hauled into five Lebanese army trucks, which drove them away as crowds at the checkpoint threw stones at them.

On Sunday, 46 SLA militiamen defected from three main towns in the same area, joining hundreds of residents who returned home, many for the first time since Israel set up the zone in 1985.

President Emile Lahoud, speaking on television, said those who cooperated with Israel will be held accountable. Lebanese law punishes collaboration with Israel with jail terms and even death.