Hundreds of handheld pagers exploded almost simultaneously across Lebanon and in parts of Syria on Tuesday, killing at least nine people, government and Hezbollah officials said. Officials pointed the finger at Israel in what appeared to be a sophisticated, remote attack.

The wave of exploding electronic devices used by Hezbollah members could be a prelude to a wider attack by Israel.

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.