The pagers began beeping just after 3:30 in the afternoon in Lebanon on Tuesday, alerting Hezbollah operatives to a message from their leadership in a chorus of chimes, melodies, and buzzes.

But it wasn’t the militants’ leaders. The pages had been sent by Hezbollah’s archenemy, and within seconds the alerts were followed by the sounds of explosions and cries of pain and panic in streets, shops and homes across Lebanon.

Powered by just a few ounces of an explosive compound concealed within the devices, the blasts sent grown men flying off motorcycles and slamming into walls, according to witnesses and video footage. People out shopping fell to the ground, writhing in agony, smoke snaking from their pockets.

Mohammed Awada, 52, and his son were driving by one man whose pager exploded, he said. “My son went crazy and started to scream when he saw the man’s hand flying away from him,” he said.

By the end of the day, at least a dozen people were dead and more than 2,700 were wounded, many of them maimed. And the following day, 20 more people were killed and hundreds wounded when walkie-talkies in Lebanon also began mysteriously exploding. Some of the dead and wounded were Hezbollah members, but others were not; four of the dead were children.