Israel threatened on Tuesday to return to war in Lebanon if its truce with Hezbollah collapses, and said this time its attacks would go deeper and target the Lebanese state itself, after the deadliest day since the ceasefire was agreed last week.

Israel and the Lebanese group Hezbollah traded fire, raising worries that their ceasefire may already be at risk. The truce, which only came into effect last week, has been a much-needed bright spot in a region blighted by over a year of conflict that has left tens of thousands dead and millions displaced across Lebanon and Gaza.

Israel said it struck targets in Lebanon on Monday evening after vowing to retaliate for an attack by Hezbollah on a military post, with both sides accusing each other of violating last week's ceasefire. At least nine people were killed by Israeli strikes on two southern Lebanese villages, according to the country's public health ministry.