BEIRUT — The Israeli military on Thursday said its warplanes fired on southern Lebanon after detecting Hezbollah activity at a rocket storage facility, the first Israeli airstrike a day after a ceasefire between Israel and Hezbollah took hold.

Israel said on Thursday that its ceasefire with Hezbollah was breached hours after Lebanese security sources said Israeli tanks attacked six areas of southern Lebanon, calling into question a truce reached after more than a year of fighting.

Israel said it conducted an air strike on a Hezbollah weapons facility on Thursday, the first since a ceasefire in the war in Lebanon took effect.The truce, which came into force on Wednesday, seeks to end a war that has killed thousands in Lebanon and sparked mass displacements in both Lebanon and Israel.