Israeli warplanes have already bombed large parts of southern Lebanon, which is says is the origin point for rockets fired into Israel by Hezbollah guerrillas.
Friday, Israel said four of its soldiers - searching border areas for Hezbollah fighters, bases and weaponds - were killed in a gunbattle with Hezbollah forces in south Lebanon. Israel says several of its soldiers were wounded and Hezbollah also sustained losses.
Witnesses say Israeli forces resumed attacks on Lebanon at daybreak. One large explosion was heard in Beirut. The Al-Arabyia TV channel said the strike had targeted Beirut's southern suburbs, a Hezbollah stronghold that has been pounded by Israeli missiles over the past few days.
The Arab satellite TV channel Al-Jazeera said one person was killed and another wounded in the airstrike – a report that has not been otherwise confirmed.
Witnesses and Hezbollah TV say Israeli aircraft targeted the town of Nabi Sheet in the eastern Bekaa valley, where Hezbollah guerillas have been known to operate. Hezbollah TV also reports Israeli airstrikes on a road and bridge near the southern port city of Tyre.
Thursday, Israeli troops met fierce resistance from Hezbollah guerrillas as they crossed into Lebanon to seek tunnels and weapons for a second straight day, and Israel has refused to rule out the possibility of a full scale invasion.
Maj. Gen. Benny Ganz, commander of Israeli ground forces, gave no indication he was feeling any pressure to stop his attacks on south Lebanon. In fact, he said they would continue to try and eliminate Hezbollah's leaders.
In an interview with CBS News chief foreign correspondent Lara Logan, Ganz said: "We try to hit the organization leadership as far as much as we can... We'll keep on trying. It's only Thursday."
Asked how long Israel's offensive against Lebanon could last, Ganz said, "It can reach months."
In other recent developments:
to hear a report from CBS News correspondent
Robert Berger, on the scene with Israeli artillery crews.
Appearing on Al-Jazeera Thursday, Hezbollah leader Sheik Hassan Nasrallah denied Israeli claims that 50 percent of his guerrillas' rocket arsenal has been destroyed.
"Hezbollah has so far stood fast, absorbed the strike and has retaken the initiative and made the surprises that it had promised, and there are more surprises," he said, warning that a Hezbollah defeat would be "a defeat for the entire Islamic nation."
Israeli troops crossed the border as part of ongoing operations to push back Hezbollah guerrillas, who have continued firing rockets into northern Israel despite more than a week of massive bombardment.
Hezbollah guerrillas fired 25 rockets into Israel on Thursday. Although they caused no casualties, the continued rocket barrage raised the question of whether Israeli air power alone can suppress them.
The guerrillas have been fighting back hard on the ground, wounding three Israeli soldiers. An Israeli unit sent in to ambush Hezbollah guerrillas also had a fierce gunbattle with a cell of militants.
The Lebanese government is under international pressure to deploy troops in the south to rein in Hezbollah, but even before the fighting, many considered it too weak to do so without deeply fracturing the country.
On Wednesday, Lebanese Prime Minister Fuad Saniora appealed for a cease-fire, saying Lebanon "has been torn to shreds."
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 if they are in an area it is striking. "Civilians might be in the area because Hezbollah is operating from civilian territory," he said.
He said thatat 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.
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.