Israeli strikes pounded targets the length of southern Lebanon on Saturday, killing at least 39 people in what authorities in Beirut described as the deadliest day since a three-week-old ceasefire with Hezbollah took effect. A separate raid hit a highway not far from Beirut, well outside the group's traditional southern strongholds.

Lebanon's National News Agency reported a sustained sequence of strikes from Tyre toward the Israeli border, with the village of Saksakiyeh taking one of the heaviest hits. The health ministry said the Saksakiyeh raid alone produced an initial toll of seven killed — among them a young girl — and 15 wounded, three of them children.

Hezbollah said in a statement that it had targeted Israeli troops in the north with drones on at least two occasions during the day, calling the attacks a response to what it described as repeated Israeli violations of the truce. The Israeli military said its air defences engaged the drones; no casualties were reported on the Israeli side.

The exchanges mark the most intense flare-up since the late-April ceasefire that paused months of cross-border fighting. The truce has done little to halt daily skirmishes in the south, but Saturday's casualty count was several times the pace seen in any 24-hour stretch since the agreement.

United Nations officials have warned for weeks that the strikes near Beirut, in particular, threaten to widen the conflict. A UN spokesperson called Saturday's roadside strike outside the capital "a very alarming development" and urged restraint.

Israel says its operations target Hezbollah commanders, weapons stores and infrastructure that the group has continued to rebuild in defiance of the ceasefire. The military has not commented on individual sites struck on Saturday but has consistently maintained that civilian casualties are the result of Hezbollah embedding in residential areas.

The escalation also complicates the parallel Iran-US negotiations on a memorandum to end the broader regional conflict. Lebanese officials have privately warned mediators that another extended cycle of strike-and-counter-strike could collapse what remains of the truce.

Aid agencies operating in southern Lebanon say the renewed bombardment has slowed an already halting return of displaced families. Roughly a quarter of buildings in 25 municipalities along the border were damaged or destroyed in the earlier round of fighting, according to satellite analysis cited by humanitarian organisations.