The leader of Hezbollah has vowed that attacks across Lebanon will be met with what he called "just punishment." Hassan Nasrallah made the promise after hundreds of mobile devices exploded. Thirty-seven people were killed and more than 3,000 wounded.

Hezbollah officials are trying to figure out how pagers across the country blew up on Tuesday.

Then, on Wednesday, they saw walkie-talkies go off.

The militants have been trading fire with Israeli forces for months.

And several fighters were among those killed.

Nasrallah laid the blame with Israel. He said: "The enemy in this operation crossed all the rules, laws and red lines. They didn't care about anything at all."

Officials looking into the attacks initially suggested a company in Hungary had built the pagers.

But the New York Times says the firm was part of an Israeli front, citing three intelligence officers.

They said at least two other shell companies were set up to mask the identities of the people making the pagers.

Israel's Defense Minister Yoav Gallant met with officers to discuss how to respond, and how to help people displaced by the fighting.

Gallant said: "Our goal is to ensure the safe return of Israel's northern communities to their homes. As time goes by, Hezbollah will pay an increasing price."

Gallant says the war has entered a "new phase" after almost a year of fighting farther south in Gaza. He says the center of gravity is "moving north."