The Israeli military said it carried out dozens of strikes against Hezbollah targets in southern Lebanon on Thursday, as both countries anxiously faced the prospect of a rapidly escalating conflict. It was one of the largest bombardments in a year of heightened clashes, according to Lebanese officials.

The airstrikes came soon after the leader of Hezbollah, a Lebanese-based militant group, vowed that “retribution will come” to Israel for the wireless device explosions that targeted his fighters and led to two days of panic in Lebanon this week.

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But even as the Hezbollah chief, Hassan Nasrallah, was promising his followers in a speech that Israel would pay, Israeli jet fighters screamed overhead, setting off sonic booms in what seemed a clear show of might.

Not long after, the skies over southern Lebanon filled with jets, and the booms that followed were from bombs. The Israeli military carried out more than 70 airstrikes across southern Lebanon, according to three senior Lebanese security officials, who requested anonymity as they were not authorized to speak to the media.

The Israeli bombardment was a marked uptick from the daily tit-for-tat attacks that has characterized the cross-border fighting for the past 11 months. But it appeared to fall short of a major escalation: there were no immediate reports of casualties and the strikes appeared to have avoided both major population centers and the country’s heartland.

Israel and Hezbollah, which is backed by Iran, an Israeli nemesis, have long been at odds, but tensions have ratcheted up since Israel’s war with another Iranian-backed group, Hamas, began in October. A day after Hamas attacked Israel, setting off the war, Hezbollah began firing rockets into Israel in a show of support.

Earlier this week, pagers and walkie-talkies widely used by Hezbollah operatives began exploding all at once across Lebanon, killing dozens and wounding hundreds. The operation has been tied to Israel, though the Israelis have not claimed responsibility for it.

Here is what else to know:

— Making his first public remarks since the device explosions Tuesday and Wednesday, Nasrallah acknowledged that his group had “endured a severe and cruel blow.” But he said Israel would “face just retribution and a bitter reckoning,” accusing the country of breaking “all conventions and laws.” He left his threat vague. “I will not discuss time, nor manner, nor place,” Nasrallah said. He also promised that the exploding-device attacks would not deter Hezbollah from continuing to launch rockets and drones at Israel in support of Hamas.

— Walkie-talkies: The Japanese company whose name was on the two-way radios that exploded said Thursday that it had discontinued that model a decade ago and had warned of fake versions.

— The exploding wireless devices that targeted members of the Lebanese armed group Hezbollah this week have set off a debate among experts in international law: Are such attacks legal? Specifically, legal scholars and advocates are asking whether it violates the laws of war to detonate secretly installed explosives in thousands of pagers and walkie-talkies when it is virtually impossible to know who else might be in the vicinity.

This article originally appeared in The New York Times.