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.

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 carried out one of its most intense bombardments against the Hezbollah militant group Thursday night, launching dozens of airstrikes over Lebanon. The aerial barrage comes just after Hezbollah's leader vowed revenge for a series of deadly device explosions that targeted the group's members this week.