The Israeli military carried out dozens of airstrikes against the Lebanese militant group Hezbollah on Thursday, one of the most intense waves of bombardment this year. The strikes came hours after Hezbollah’s leader vowed that “retribution will come” to Israel after audacious attacks on Hezbollah’s pagers and walkie-talkies.

The device explosions killed at least 37 people and left many Israelis and Lebanese fearful of a worsening conflict between Hezbollah and Israel.

In his first speech since the devices blew up on Tuesday and Wednesday, Hassan Nasrallah, the Hezbollah leader, conceded that his group had “endured a severe and cruel blow.” He accused Israel of breaking “all conventions and laws” and said that it would “face just retribution and a bitter reckoning.”

But he did not describe how Hezbollah, which Iran backs, might retaliate, saying, “I will not discuss time, nor manner, nor place.”

Israel has not confirmed or denied responsibility for the device explosions, although current and former defense and intelligence officials who were briefed on the attacks say Israel was behind them.