U.N. peacekeepers in Lebanon urged immediate de-escalation as hostilities rumbled on at the Lebanese-Israeli border on Friday, following Israel's most intense airstrikes in nearly a year of conflict with the Iran-backed Hezbollah.

Israel launched a wave of airstrikes against Hezbollah targets in southern Lebanon, just as the militant group’s leader said two days of exploding pagers and walkie-talkies amounted to a declaration of war.

The strikes came hours after Hezbollah’s leader vowed that “retribution will come” to Israel for the explosions of Hezbollah members’ hand-held devices. At least 37 people were killed and more than 2,900 others injured in those explosions on Tuesday and yesterday. Here’s the latest.