The Israeli force crossed the border as part of ongoing operations to clear out Hezbollah infrastructure along a small band on the Lebanese side, the army said. The army did not provide numbers or conditions of the casualties.

Meanwhile, Israel hinted at a full-scale invasion, and U.N. Secretary-General
Kofi Annan told the Security Council that "hostilities must stop." He also condemned Israel's "excessive use of force" against Lebanon.

"There are serious obstacles to reaching a cease-fire or even to diminishing the violence quickly," Annan said.

He added that the fighting had triggered a humanitarian crisis.

Israeli warplanes launched new airstrikes on Beirut's southern suburbs, a Hezbollah stronghold, shortly after daybreak, followed by strikes in the guerrillas' heartland in the south and eastern Bekaa Valley.

The strikes followed bombings Wednesday that killed as many as 70 people, according to Lebanese television, making it the deadliest day since the fighting began July 12.

Russia sharply criticized Israel over its onslaught against Lebanon, now in its ninth day, sparked when Hezbollah militants captured two Israeli soldiers. The Russian Foreign Ministry said Israel's actions have gone "far beyond the boundaries of an anti-terrorist operation" and repeating calls for an immediate cease-fire.

At least 306 people have been killed in Lebanon since the Israeli campaign began, according to the security forces control room that collates casualties. In Israel, 29 people have been killed, including 14 soldiers. The U.N. has said at least a half- million people have been displaced in Lebanon.

About 40 U.S. Marines landed in Beirut to help Americans onto the USS Nashville, which will carry 1,200 evacuees bound for Cyprus in the second mass U.S. exodus from Lebanon. Thousands of Europeans also fled on ships — continuing one of the largest evacuation operations since World War II. An estimated 13,000 foreign nationals have been evacuated.

Israel's series of small ground forays across the border have aimed to push back Hezbollah guerrillas who have continued firing rockets into northern Israel despite more than a week of massive bombardment — raising the question of whether air power alone can suppress them. Guerrillas fired 25 rockets into Israel on Thursday, which caused no casualties.

But the guerrillas have been fighting back hard on the ground, wounding three Israeli soldiers Thursday, a day after killing two. An Israeli unit sent in to ambush Hezbollah guerrillas also had a fierce gunbattle with a cell of militants.

In another clash, just across the border from the Israeli town of Avivim, guerrillas fired a missile at an Israeli tank, seriously wounding one soldier. Hezbollah said its guerrillas destroyed two tanks trying to enter the Lebanese border village of Maroun al-Ras, across from Avivim.

Israel has mainly limited itself to attacks from the air and sea, reluctant to send in ground troops on terrain dominated by Hezbollah.

But an Israeli army spokesman refused to rule out the possibility of a full-scale invasion. Israel broadcast warnings Wednesday into south Lebanon, telling civilians to leave the region — a possible prelude to a larger Israeli ground operation.

"There is a possibility — all our options are open. At the moment, it's a very limited, specific incursion but all options remain open," Capt. Jacob Dallal, an Israeli army spokesman, told The Associated Press on Wednesday.

Leaflets dropped Wednesday night warned the population that any trucks traveling in Lebanese towns south of the Litani River would be suspected of carrying weapons and rockets and could be targeted by Israeli forces.

The Lebanese government is under international pressure to deploy troops in the south to rein in Hezbollah guerrillas — but even before the fighting, many considered it too weak to do so without deeply fracturing the country.

An Italian newspaper quoted Lebanese Prime Minister Fuad Saniora on Thursday as making his strongest statement yet against the Shiite militant group. But Saniora's office quickly said he was misquoted.

The Milan-based Corriere della Sera quoted him as saying in an interview that Hezbollah has created a "state within a state," adding: "The entire world must help us disarm Hezbollah. But first we need to reach a cease-fire."

Saniora later issued a statement denying the remarks. He said he told the paper the international community must help press Israel from Chebaa Farms, a small border area that Lebanon claims and Hezbollah points to as proof of the continued need for armed resistance.

Saniora told the paper that "the continued presence of Israeli occupation of Lebanese lands in the Chebaa Farms region is what contributes to the presence of Hezbollah weapons. The international community must help us in (getting) an Israeli withdrawal from Chebaa Farms so we can solve the problem of Hezbollah's arms," the statement said. There was no immediate comment from the newspaper.

On Wednesday, Saniora appealed for a cease-fire, saying Lebanon "has been torn to shreds." Warplanes pounded southern areas where Hezbollah operates, but civilian residential neighborhoods bore the brunt, with dozens of houses destroyed.

Dallal said Israel had hit "1,000 targets in the last eight days — 20 percent were missile-launching sites and the rest were control and command centers, missiles and so forth."

Brig. Gen. Ido Nehushtan insisted the Israeli army never targets civilians but has no way of knowing whether they are in an area it is striking. "Civilians might be in the area because Hezbollah is operating from civilian territory," Nehushtan said.

He said that Hezbollah has fired more than 1,100 rockets at civilian areas in Israel since the fighting began and that 12 percent — or about 750,000 people — of Israel's population lives in areas that can be targeted by the guerrillas.

Israel said its airstrikes so far have destroyed about half of Hezbollah's arsenal — and it has been trying to take out its top leaders.

The Israeli military said aircraft dropped 23 tons of explosives on what it believed was a bunker for senior Hezbollah leaders in the Bourj al-Barajneh neighborhood of Beirut between 8 p.m. and 9 p.m. Wednesday.

Hezbollah said none of its members was hurt and denied a leadership bunker was in the area, saying a mosque under construction was hit. It has a headquarters compound in Bourj al-Barajneh that is off limits to Lebanese police and army, so security officials could not confirm the strike.

Israel's U.N. Ambassador Dan Gillerman told CNN his country would not comment about the attack until it is sure of all the facts. But he added, "I can assure you that we know exactly what we hit. ... This was no religious site. This was indeed the headquarters of the Hezbollah leadership."

On Thursday, Israeli jets struck houses believed used by Hezbollah officials in the town of Hermel in the western Bekaa Valley, wounding at least three.

Israeli warplanes also destroyed a five-story residential and commercial building that reportedly once held a Hezbollah office in the Bekaa Valley city of Baalbek, a Hezbollah stronghold, witnesses said. There was no immediate word on casualties.

Two civilians were killed late Wednesday in strikes on bridges in Lebanon's far north, near Tripoli, the National News Agency said.

Israeli jets also raided a detention center in the southern town of Khiam Thursday, witnesses and local TV said. The notorious Khiam prison, formerly run by Israel's Lebanese militia allies during its occupation, was destroyed in four bombing runs, they said.

International pressure mounted on Israel and the United States to agree to a cease-fire. The destruction and rising death toll deepened a rift between the U.S. and Europe.

The Bush administration is giving Israel a tacit green light to take the time it needs to neutralize Hezbollah, but the Europeans fear mounting civilian casualties will play into the hands of militants and weaken Lebanon's democratically elected government.

U.N. High Commissioner for Human Rights Louise Arbour criticized the rising toll, saying the shelling was invariably killing innocent civilians.

"International law demands accountability," she said in Geneva. "The scale of the killings in the region, and their predictability, could engage the personal criminal responsibility of those involved, particularly those in a position of command and control."