A Hezbollah drone attack on an army base in central Israel killed four soldiers and severely wounded seven others in the deadliest strike by the militant group since Israel launched its ground invasion of Lebanon nearly two weeks ago.
Dozens more were injured in the attack, which penetrated Israel's Iron Dome defence system and hit the Israeli Defense Forces base near Binyamina, north of Tel Aviv.
Here is what we know so far.
Where did the drone strike hit?
The IDF camp near Binyamina is about 55 kilometres from the Lebanese border, 60km north of Tel Aviv and about 30km south of the coastal city of Haifa.
Hezbollah said the target hit on Sunday was a Golani Brigade training camp.
The IDF regards the Golani Brigade as one of its elite infantry units.
Haifa is home to another military base which has also been the target of Hezbollah drone attacks.
What do we know about what happened?
Video footage broadcast on Israeli TV showed wounded people being ferried from helicopters into ambulances.
Haifa's Rambam Medical Centre released video of a wounded person on a stretcher being quickly wheeled inside.
The IDF said four soldiers were killed in the attack and seven more were severely injured.
Israel's Magen David Adom ambulance service said the total number of injured people, including minor injuries, was 61.
Israeli volunteer rescue service United Hatzalah reported that its teams in Binyamina assisted "over 60 wounded people" who were suffering from mild to critical injuries.
Lebanese militant group Hezbollah said the attack was carried out by a "squadron of attack drones" and warned of more strikes to come.
Hezbollah described the operation as "complex" and said it had launched dozens of missiles to "keep Israeli defence systems busy" while the drones were in the air.
The drones "exploded in the rooms where dozens of officers and soldiers of the Israeli enemy were present", a Hezbollah statement said.
Times of Israel diplomatic correspondent Lazar Berman said the attack featured two drones launched by Hezbollah, and that Israel's warning systems had failed.
"It was the same type of suicide drone that Hezbollah has been firing for a year now," he told ABC News Channel.
"I can say one of the drones was shot down, the other one Israel chased with fighter planes [and] with helicopters and it dropped off the radar.
"The assumption was that it had crashed and therefore no sirens were sounded and that is why the soldiers were caught and that is why so many gathered together."
Berman said Israeli authorities would be investigating the failure of the warning system to make sure this "doesn't happen again".
A military helicopter drops off wounded patients in Haifa. (Reuters: Rami Shlush )
The IDF said the families of the dead and wounded had been notified and said it would release their names later.
"The IDF shares in the grief of the bereaved families and will continue to accompany them," it said in a statement.
In another apparent attack, Hezbollah also said it launched missiles at an IDF "maintenance and rehabilitation base", south of Haifa.
The conflict between Hezbollah and Israel reignited a year ago after the Lebanese militant group began firing missiles and rockets into northern Israel in the wake of the October 7 terror attack by Hamas in the south of the country.
Sunday's drone attack came against the background of continuing fighting in southern Lebanon between Israeli and Hezbollah forces, and Israeli attacks on what it says are Hezbollah targets elsewhere in Lebanon, including in the capital Beirut.
Hezbollah has warned Israelis to stay away from defence bases for the foreseeable future, while the IDF has warned people in Lebanon to leave areas where Hezbollah is operating.
Hezbollah is listed as a proscribed terrorist organisation in Australia
How did the drone or drones get through?
Israel's Iron Dome has been described as one of the most effective air defence systems on the planet.
It is designed to fend off short-range rocket and missile attacks from neighbouring militant groups by firing its own interceptor missiles to take them out.
Israel's Iron Dome intercepts rockets over the city of Ashkelon. (Reutesr: Amir Cohen)
But firing missiles and launching drones simultaneously can overwhelm the system.
Counter-terrorism expert and senior fellow at the Washington Institute Matthew Levitt said the success of the attack came as a surprise to experts because the Iron Dome had been "so successful to date".
"Part of the brilliance and also the Achilles heel of the system is it identifies targets quickly … but it can be overwhelmed with volume," he said.
"The big fear of the Hezbollah war with Israel is that [Hezbollah] will shoot 500, up to 1,000 rockets at a time.
"We haven't seen that yet. But in this episode one of the drones got through —others were shot down — with devastating effects."
Dr Levitt said it was too early to know why sirens and warnings were not triggered by the drones.
"No matter how you slice it, it was a tragedy and a failure of the Israeli system," he said.
"We have come to anticipate that the Israeli system will work every single time. No system works every single time."
An investigation into the attack will aim to uncover why Israel's Iron Dome defence system was not activated.
"We will study and investigate how an unmanned aircraft penetrated without warning," an IDF spokesperson said in a statement.
"We will learn and improve."
ABC/wires