BEIRUT — Israel pummeled Lebanon with airstrikes Monday that killed 492 people and left more than 1,600 injured, according to the Lebanese health ministry, marking the deadliest day for Lebanon since Israel and the militant group Hezbollah ramped up their exchange of fire nearly a year ago.

       In a dramatic escalation, Israel said it struck 1,300 targets in Lebanon, carrying out what an Israeli military spokesman called “extensive, precise strikes.” Israeli Prime Minister Benjamin Netanyahu, who on Sunday vowed that Israel’s military would take “whatever action is necessary” to eliminate the threat across Israel’s northern border with Lebanon, said Monday that Israel does not “wait for the threat — we take action before it.”