BEIRUT — Israeli airstrikes hit central Beirut for the first time Saturday and cross-border rocket barrages struck deeper inside Israel, reaching the previously unscathed city of Tiberias as the confrontation between Hezbollah guerrillas and the Jewish state spiraled toward all-out war.
Fueling fears that the conflict could spill over into regional strife, Israeli officials asserted that Iranian personnel had helped fire a missile Friday that crippled an Israeli naval vessel off the coast of Lebanon and killed at least three sailors. Israel and the United States have accused Iran, Hezbollah's chief patron, of bearing ultimate responsibility for the Shiite Muslim militant group's actions.
With diplomacy yielding little fruit, Israeli forces and Hezbollah traded heavy blows for a fourth day. Israeli warplanes pounded targets across Lebanon, killing dozens of people, including fleeing families, and demolishing more infrastructure and Hezbollah offices.
The planes swooped in off the Mediterranean on Saturday afternoon to attack grain silos, ports and a lighthouse near the American University of Beirut. Massive clouds of smoke billowed into the sky over the coast; eerily quiet streets in the capital grew even more deserted as night fell.
Civilians on both sides bore the brunt of the violence. In southern Lebanon, an Israeli airstrike killed at least 15 people fleeing the fighting, 12 of them children. Lebanese officials said more than 100 people had been killed in the four days of airstrikes. Four Israeli civilians and 11 military personnel have died.
Two rocket barrages hit the Israeli resort city of Tiberias, injuring eight people and sending sunbathers fleeing from the shores of the Sea of Galilee.
The strike, the first rocket attack in Tiberias since the 1973 Yom Kippur War, heightened Israel's anxiety that many of its urban centers, including the densely populated outskirts of Tel Aviv, are now within range of Hezbollah's weapons.
At least 90 rockets fell Saturday across northern Israel, pushing the total since the fighting broke out to more than 400, the Israeli military said. Tens of thousands of northern Israel's 750,000 people are spending much of their time in bomb shelters or at home, venturing out only to stock up on supplies. Many others have sought refuge in the south.
Even some Orthodox Jews, whose religious precepts forbid them to drive on the Sabbath, climbed behind the wheel Saturday to escape the rocket fire.
In the northern town of Carmiel, residents abandoned an apartment building shortly before it took a direct hit.
"They left in time and were saved. There is the proof," neighbor Yair Bomler told Israel's Channel 2, gesturing toward the rubble.
The fighting was triggered by a cross-border raid Wednesday in which Hezbollah killed eight Israeli soldiers and captured two.
Israel declared the raid an act of war by Lebanon, whose leaders say they are powerless to rein in the militant group, which is also a partner in the government. In by far the strongest statement to emerge from the Lebanese administration -- largely silent during the last four days -- Prime Minister Fouad Siniora implored the international community to save his country from ruin.
"We call for an immediate cease-fire backed by the United Nations," an impassioned Siniora said at a news conference Saturday evening in Beirut.
In a counterweight to the enraged declaration of war issued the previous night by Hezbollah chief Sheik Hassan Nasrallah, Siniora spoke with despair of civilian suffering.
"Destruction is raining down around the clock," he said.
The Arab League said after an emergency meeting in Cairo that the peace process had failed in the Middle East, and it called on the U.N. Security Council to intervene.
Israel has asserted that Iran is a driving force behind Hezbollah's attacks. On Saturday, Israeli officials made their most specific allegation yet of such involvement, saying an Iranian military or technical team helped Hezbollah fire an Iranian-made radar-guided missile to strike the Israeli warship.
"We have particular knowledge that they assisted them," a senior military official said, speaking on condition of anonymity. The official said more than 100 Iranian troops, including members of the elite Republican Guard, were in Lebanon and assisting Hezbollah.
In a statement issued by its embassy in Beirut, Iran denied having troops in Lebanon or playing any role in the warship strike. State television in Iran said President Mahmoud Ahmadinejad condemned the Israeli offensive. "The Zionist regime behaves like Hitler," it quoted him as saying.
The attack on the Israeli ship left three sailors dead and one missing. The ship had been helping enforce the Israeli blockade of the Lebanese coast begun Thursday; it returned to Israel under escort Saturday.
Israel said the use of a sophisticated C-802 missile showed that the world had been too slow to recognize the threat posed by Iran's arming of Hezbollah.