A wave of deadly explosions of pagers and other electronic devices carried by militants in Lebanon has sharply heightened Pentagon concern about a potential ground war erupting in southern Lebanon between Israel and Hezbollah.

U.S. officials say Israel warned U.S. Defense Secretary Lloyd Austin in a call Tuesday that a military operation was going to take place in Lebanon

By Laila Bassam and Maya Gebeily BEIRUT/JERUSALEM (Reuters) -Israeli warplanes carried out late on Thursday their most intense strikes on southern Lebanon in nearly a year of war, heightening the conflict between Israel and Lebanese armed group Hezbollah amid calls for restraint.

Israel carried out dozens of airstrikes across southern Lebanon today, one of the most intense bombardments in the country this year. The strikes came hours after Hezbollah’s leader vowed that “retribution will come” to Israel for the explosions of Hezbollah members’ hand-held devices.

Lebanon’s death toll from a series of walkie-talkie and pager explosions this week rose to 37, according to local authorities, an illustration of the devastation wrought by a wave of suspected Israeli attacks against Hezbollah militants.

Hezbollah's leader says the mass explosions in Lebanon on the group's communications devices was a "severe blow" and said Israel has crossed a "red line."

Israeli forces late Thursday carried out their most intense strike on southern Lebanon in nearly one year of war, increasing tensions between the two countries despite international calls for calm. In the operation,