Israel launched a series of intense airstrikes in southern Lebanon early Sunday in what it said was a pre-emptive strike against the Hezbollah militant group, threatening to trigger a broader regionwide war that could torpedo efforts to forge a cease-fire in Gaza.

Warning sirens rang in northern Israel soon and Lebanese media reported strikes in the country's south. Israel's Ben Gurion International Airport outside Tel Aviv began diverting incoming flights and delaying others due to takeoff Sunday after the Israeli airstrikes in Lebanon.

Israeli forces struck southern Lebanon in the early hours of Sunday in what they say was a “preemptive” attack launched when they detected Hezbollah preparing to attack northern Israel. Hezbollah launched “a large number of missiles” towards Israel in what it says is a response to the killing of commander Fuad Shukr at the end of July.

Hezbollah launched more than 100 rockets at Israel on September 4, the largest escalation since the group launched several hundred rockets on August 25. The attacks took place amid shifts on other fronts as Israel handles Iranian-sponsored threats.

Hezbollah released a statement that the rocket barrage toward Israel was done as retaliation for an earlier Saturday Israeli strike.