The Israeli military said it was “currently striking Hezbollah terror targets deep inside Lebanon” but provided no further details. There was no immediate comment from the heavily armed, Iranian-backed Hezbollah.

Hezbollah and the Israeli military have been exchanging fire along Lebanon’s southern border since October, when Hezbollah launched rockets at Israel in support of its Palestinian ally Hamas, which is it at war with Israel in the Gaza Strip.

Israeli strikes had been mostly limited to the southern border region of Lebanon, although they have edged further north in recent weeks. Monday’s bombardment represented a broadening of Israel’s campaign, a Lebanese security source said.

Lebanese television station Al-Jadeed broadcast images of plumes of smoke emanating from the area of Baalbek on Monday.

The Baalbek region, in Lebanon’s Bekaa Valley, is known to be a political stronghold of Hezbollah but is also home to ancient Roman ruins and is an important agricultural and transport hub for Lebanon.

(Reporting by Laila Bassam in Beirut and Ari Rabinovitch in Jerusalem; writing by Maya Gebeily; editing by Gareth Jones and Mark Heinrich)