Israel and Hezbollah accelerated their cross-border attacks overnight into Sunday with their leaders exchanging saber-rattling threats in a rapidly deteriorating situation that has the adversaries as close to full-out war as they have been in their nearly yearlong conflict.

A leader of the Iranian-backed militia said its latest barrage was “just the beginning,” and an Israeli military official said, “Our strikes will intensify.”

Israel and the Hezbollah militant group exchanged heavy fire across the Lebanese border on Sunday, fueling fears of a wider conflict in the region.