Israel has carried out major bombing in Lebanon as the IDF says it was targeting the militant group Hezbollah, who has fired back. The U.S. has warned both sides against an escalation of any kind as fears of a wider war in the Middle East grow.

Israel carried out one of the most intense bombardments of the past year, as warplanes launched 70 airstrikes, Lebanese security officials said. The barrage came shortly after Hezbollah’s leader vowed to respond after explosions of pagers and walkie-talkies killed at least 37 people.

First came two days of exploding pagers and walkie-talkies used by Hezbollah — deadly attacks pinned on Israel that also maimed civilians around Lebanon. Hezbollah’s leader vowed to retaliate , and on Friday the militant group launched dozens of rockets into northern Israel.