Israel Strengthens Its Forces in South Lebanon : Mideast: Ground attacks on guerrillas may be planned. Lebanese say 500,000 have fled the region.

Israel substantially strengthened its forces in southern Lebanon on Thursday, sending in more tanks, artillery and infantry in apparent preparation for ground attacks against militant Muslim guerrillas there.

Israeli warplanes, artillery and naval gunboats again attacked scores of villages believed to have housed guerrillas belonging to the pro-Iranian Hezbollah, or Party of God, and to radical Palestinian groups.

The bombardment drove thousands more villagers north toward Beirut or east toward Syria, and Lebanese authorities estimated that 500,000 people have now fled the region, calling it a “human catastrophe of tragic magnitude.”

More than 300 villages remain under attack in southern Lebanon, and 75 have been destroyed, said a Lebanese army spokesman in Beirut. The bombardment from air, land and sea remained intense, military sources said, and in some places nine shells were landing each minute.

Twelve people were killed and 62 wounded, according to Lebanese officials, who put their total casualties at more than 100 dead since the Israeli offensive began Sunday.

The guerrillas hit back sporadically, firing salvos of Katyusha rockets into northern Israel on Thursday morning and several more again in the evening, an Israeli military spokesman said. Three civilians were wounded by the rockets, the spokesman said; Israeli casualties stand at three dead, about 30 wounded.

Prime Minister Yitzhak Rabin, dismissing as “inconclusive” American efforts to arrange a cease-fire in the region, declared that Israel will not halt its campaign except “on terms satisfactory to the government of Israel.”

“The main goal was to achieve (a situation) where the communities and residents in Israel will not be hostages of the Hezbollah,” Rabin said at a northern air base. “As long as these goals have not been reached, the Israel Defense Force’s action will not be stopped.”

Lt. Gen. Ehud Barak, Israeli chief of staff, called the current confrontation with Hezbollah a “test of wills” as he visited units heading into Israel’s self-declared “security zone,” the nine-mile-deep buffer area Israel established in 1985 inside Lebanon.

“As you can see, there are Katyushas being fired,” Barak said. “As long as the attacks have not been stopped, and a situation has not been created in which Katyushas are not fired on our communities . . . the (operation) will continue.”

Despite apparent preparations for ground attacks on Hezbollah units in the region, Israel continues to hope the flood of refugees it has created, now more than 10% of Lebanon’s population, will force the government of President Elias Hrawi in Beirut to curb the guerrillas. That will require the assistance of Syria, which maintains 40,000 Syrian troops in Lebanon, and Damascus until now has been a supporter of Hezbollah.

The United States has been working to arrange a cease-fire in advance of Secretary of State Warren Christopher’s visit to the Middle East next week, diplomatic sources said. But it was unable to secure pledges sought by Israel from Lebanon and Syria to control Hezbollah and ensure Israeli security.

“If the Americans, or others, can guarantee that there will be no Katyusha attacks on our northern towns and settlements, then we will immediately cease our shelling,” said Oded Ben-Ami, a senior Rabin aide. “So far, no one has been able to guarantee that.”

Before Israel last Sunday began its operation, which it has characterized as a retaliatory action, guerrillas had killed seven Israeli soldiers in the security zone and increased their rocketing of Israel’s northern communities.

But discussions were under way among Lebanese, Syrian and Iranian leaders in Damascus, and Lebanese Prime Minister Rafik Hariri was reported discussing possible compromises with Christopher by telephone.

Arab League foreign ministers will hold an emergency meeting today in Damascus and are likely to offer humanitarian aid for the swelling tide of refugees, but there is probably little they can do otherwise.

Foreign Minister Shimon Peres, nonetheless, said he expects a halt to the fighting before the Christopher visit, and diplomatic sources said that the secretary has made it clear to Rabin that, if the fighting were continuing when he arrived in Jerusalem on Sunday, his trip would likely prove futile in advancing the Arab-Israeli negotiations.

On the battlefield, Israel appeared to be preparing for a new phase of the offensive with ground forces likely to be sent in pursuit of Hezbollah units still operating in the hills and woods of southern Lebanon despite the nonstop bombardment.

About 100 tanks, armored personnel carriers and self-propelled artillery pieces accompanied by truckloads of troops crossed into southern Lebanon on Thursday with more on the roads moving toward the border; military spokesmen declined to discuss deployment plans.