JERUSALEM (Reuters) -- Hezbollah launched hundreds of rockets and drones against Israel on Sunday in retaliation for the assassination of a senior commander in Beirut last month, the Iranian-backed movement said, as Israel's Cabinet met to prepare a response.

Israeli jets hit targets in Lebanon shortly before the strikes, as the military assessed that Hezbollah was preparing to begin the barrage, the military said.

Hezbollah said it had launched more than 320 Katyusha rockets toward Israel and hit 11 military targets. It said the barrage had completed "the first phase" of its response to the assassination of Fuad Shukr, a senior commander, in Beirut but that the full response would take "some time."

Israel's Cabinet was to meet at 7 a.m., Prime Minister Benjamin Netanyahu's office announced.

Defense Minister Yoav Gallant said Israel would do whatever necessary to defend itself.

"We have conducted precise strikes in Lebanon in order to thwart an imminent threat against the citizens of Israel. We are closely following developments in Beirut, and we are determined to use all the means at our disposal in order to defend our citizens," Gallant said in a statement.

Most of the Israeli strikes were hitting targets in southern Lebanon, but the military was ready to strike anywhere there was a threat, an Israeli military spokesperson said.

Gallant declared a state of emergency, and flights to and from Ben Gurion airport in Tel Aviv were suspended, but the airports authority said normal operations were expected to resume by 7 a.m.

In northern Israel, warning sirens sounded and multiple explosions were heard around several areas as Israel's Iron Dome aerial defense system shot down rockets coming from southern Lebanon. Israel's Magen David Adom ambulance service said it was on high alert all over the country.

The Israeli military issued civil defense instructions limiting gatherings but authorizing people to go to their workplaces as long as they were able to reach air raid shelters quickly. There were no casualties immediately reported in Israel, according to the ambulance service.

A resident of the southern Lebanese town of Zibqeen, some 7 kilometers from the border, told Reuters it was the first time he had awakened "to the sound of planes and the loud explosions of rockets -- even before the dawn prayer. It felt like the apocalypse."

Expectations of an escalation between the two sides had risen since a missile strike in the Israeli-occupied Golan Heights last month killed 12 youngsters and the Israeli military assassinated Shukr in Beirut in response.

The escalation has drawn fears of a wider regional conflict, potentially involving both the United States and Iran. President Joe Biden was following events closely, the White House said.

"At his direction, senior US officials have been communicating continuously with their Israeli counterparts. We will keep supporting Israel's right to defend itself, and we will keep working for regional stability," said National Security Council spokesperson Sean Savett.

The strikes came as negotiators were meeting in Cairo in a last-ditch effort to conclude a halt to fighting in Gaza and a return of Israeli and foreign hostages in exchange for Palestinian prisoners.

Hezbollah fired missiles at Israel immediately after the Oct. 7 attacks by Hamas gunmen on Israel. Hezbollah and Israel have been exchanging fire constantly ever since, while avoiding a major escalation as war rages in Gaza to the south.