At least 23 people, all of them Syrian and most of them women or children, were killed in an Israeli strike on a three-story building in the eastern Lebanese town of Younine late on Wednesday, Mayor Ali Qusas told Reuters.
Lebanon is home to around 1.5 million Syrians who fled the civil war there.
Lebanon's state-run news agency said the airstrike occurred near the ancient city of Baalbek, in the eastern Bekaa Valley running along the Syrian border.
The agency quoted Qusas as saying that the bodies of 23 Syrian citizens were pulled from under the rubble. He said four Syrians and four Lebanese were wounded.
Israeli airstrikes overnight hit around 75 Hezbollah targets in the Bekaa Valley and southern Lebanon, including weapons storage facilities and ready-to-fire launchers, the Israeli military said on Thursday.
Israel has made a priority of securing its northern border and allowing the return there of some 70,000 residents displaced by near-daily exchanges of fire, which Hezbollah initiated a year ago in solidarity with the Palestinian group Hamas in Gaza.
Israel widened its airstrikes in Lebanon on Wednesday and at least 72 people were killed, according to a Reuters compilation of Lebanese health ministry statements. The ministry earlier said at least 223 were wounded.
Around half a million Lebanese have fled their homes and hospitals have been overwhelmed with the wounded.
Israel's military chief said a ground assault was possible, raising fears the conflict could spark a wider Middle East war.
