BEIRUT, Lebanon – Israeli troops punched into south Lebanon on Wednesday as warplanes flattened houses and buildings including one thought to hold Hezbollah’s top leaders, intensifying an offensive despite mounting international pressure and a Lebanese appeal to spare the country further death and devastation.

The Israeli incursion into Lebanon came before dawn Wednesday, when troops clashed with guerrillas near the coastal border town of Naqoura. The troops later pulled back across the border, though witnesses reported two tanks remained about 500 yards inside Lebanon.

In the village of Srifa, airstrikes flattened 15 houses after rockets were fired from the area. More houses were bombed in the nearby town of Salaa and the Hezbollah stronghold of Baalbek.

Israel broadcast warnings into south Lebanon telling civilians to leave the region, a possible prelude to a larger Israeli ground operation.

Hezbollah, meanwhile, fired rockets into the Israeli Arab town of Nazareth, killing two Arab brothers, ages 3 and 9, as they played outdoors. Nazareth is where Jesus is said to have spent his boyhood.

International pressure mounted on Israel and its key supporter, the United States, to agree to a cease-fire. The rising death toll and scope of the destruction deepened a rift between the United States and Europe, and humanitarian agencies were sounding the alarm over a pending catastrophe with a half million people displaced in Lebanon.

Prime Minister Fuad Saniora, whose weak government has been unable to fulfill a U.N. directive to disarm Hezbollah and put its army along the border with Israel, issued an urgent appeal for a cease-fire. He said his country “has been torn to shreds,” and pointedly criticized the U.S. position that Israel acts in self-defense.

“Is this what the international community calls self-defense?” a stern-looking Saniora asked a meeting of foreign diplomats including U.S. Ambassador Jeffrey Feltman. “Is this the price we pay for aspiring to build our democratic institutions?”

Israel vowed to press the offensive in Lebanon until it destroys the militant Shiite guerrillas’ vast arsenal of missiles and drives Hezbollah fighters far from its northern border.

Israel said its airstrikes had destroyed “about 50 percent” of Hezbollah’s arsenal. “It will take us time to destroy what is left,” Brig. Gen. Alon Friedman, a senior army commander, told Israeli Army Radio.

Israel also has begun calling up military reservists, an indication that it might be preparing to step up ground operations, the Los Angeles Times reported.

At the close of the eighth day of fighting, a total of 29 people had been reported killed on the Israeli side of the border, including 14 soldiers and 15 civilians.

Saniora said about 370 people had died in Lebanon, 1,000 wounded and half a million were displaced.