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Hezbollah leader Hassan Nasrallah said on Tuesday that the group's retaliation for the assassinations of Ismail Haniyeh and Fouad Shukr was coming and would be carefully calculated.
It came as six people were killed in Lebanon and seven were injured in Israel after Hezbollah and the Israeli army exchanged fire across the border.
Nasrallah was unclear on what the group would do.
“We will respond, but carefully and slowly. Our response is coming. It will either be by ourselves or collectively with the axis,” he said, referring to the Axis of Resistance – an alliance of Iran-backed groups opposed to Israel and the US.
He was speaking at an event to mark a week since Hezbollah commander Mr Shukr was killed in an Israeli attack on Beirut.
“The Israelis' anticipation over the past week is part of the punishment, part of our response, and part of the battle,” Nasrallah said.
“Hezbollah will respond, Iran will respond, Yemen will respond, and the enemy is waiting and watching, calculating every move as a response.
“This is a major battle and this is a dangerous targeting and the resistance cannot, whatever the consequences, ignore it.
“Israel is the one who decided escalation. We have been very guarded over Lebanon and our country’s interests.”
Israel has been on high alert for attacks from Iran and Hezbollah since last week after its killing of Mr Shukr in Beirut and Hamas leader Mr Haniyeh in Tehran – acts which Israel said were in retaliation for the Majdal Shams attack.
Nasrallah said the group's attacks on Israel in the last few days did not constitute its retaliation.
But he did say Hezbollah had hit “new targets on new bases and new settlements”.
Nasrallah pointed out that Hezbollah drones were able to fly far into Israeli territory on Tuesday despite it being on high alert.
Hezbollah has said it will end its cross-border conflict with Israel when a ceasefire is agreed in Gaza, where more than 39,600 people have been killed, according to the enclave's Health Ministry, since the Hamas-led October 7 attack that killed about 1,200.
Nasrallah reiterated that Israeli Prime Minister Benjamin Netanyahu had no interest in a ceasefire with Hamas and sought only to displace the people of Gaza.
The escalating tension came during the most critical military phase since October, when Hezbollah and other Iran-allied groups across the Middle East started attacking Israeli targets in support of their ally Hamas in the Gaza Strip.
An Israeli strike on the southern Lebanese town of Meifadoun, near the city of Nabatieyeh, killed five people, Lebanon’s Health Ministry said. Separately, one person was killed and another seriously injured in an Israeli raid on the outskirts of the villages of Odaisseh and Rabb El Thalathin.
The Israeli army said it had attacked a “Hezbollah military structure” near Nabatieyeh. Hezbollah announced the death of five of its fighters on Tuesday evening.
In Israel, several people were injured by an Israeli missile interceptor attempting to deflect a barrage of projectiles launched by Hezbollah, the army said.
At least seven were injured during the overall barrage – one of whom was critically injured. The Israeli army did not clarify how many of the seven were injured by the failed interceptor missile.
Hezbollah announced it had launched a squadron of attack drones at the headquarters of the Golani Brigade and Egoz Unit 621, saying they had “achieved confirmed casualties”.
The Israeli army acknowledged “a number of hostile [unmanned aerial vehicles] were identified crossing from Lebanon” but that only one was successfully intercepted.
A man in his 40s was in a critical condition after being hit while driving by one of the Israeli interceptor missiles launched to meet Hezbollah's barrage.
“A preliminary investigation of the incident indicates that it was the fall of an interceptor that missed the target and hit the ground,” the military said.
Ambulance teams “have been dispatched to handle three locations in the Western Galilee, from which a total of seven casualties were evacuated: one in critical condition, one in mild-to-moderate condition, and five in mild condition”, Israel's national ambulance service said.
Air raid sirens sounded in 16 communities across northern Israel on Tuesday afternoon.
Videos circulated on social media showed the damage from the rocket barrage on the military base, with buildings and cars on fire.
The Lebanese group said the attack was in response to the Israeli assassination of Hezbollah member Ali Jawad in the southern Lebanese village of Ebba on Monday.
The Israeli army said Mr Jawad was a commander in Hezbollah’s elite Radwan force.
It came as Israeli fighter jets broke the sound barrier above Beirut in the minutes before Nasrallah's speech.
The disturbance shook the windows of The National’s Beirut bureau and were heard and felt throughout the city and its suburbs. Residents of Beirut said it was the loudest series of sonic booms to hit the Lebanese capital since fighting broke out in October.
The fallout from a deadly rocket attack on the Syrian Druze town of Majdal Shams in the occupied Golan Heights in late July, which killed a dozen children, has left the already volatile region on the course for an all-out confrontation.
Israel said Hezbollah's Mr Shukr orchestrated that attack, while the Lebanese group has denied involvement, instead claiming an Israeli interceptor missile was responsible for the children's deaths.
The two events marked an escalation with major repercussions for the Middle East in general and the Gaza ceasefire talks in particular.
Nasrallah said last week that the red lines crossed by Israel in its assassinations of Mr Shukr and Mr Haniyeh would usher in a “new phase” of the multifront conflict that will make Israel “weep”.
UK Foreign Secretary David Lammy has spoken to Iranian Foreign Minister Ali Bagheri Kani, asking Tehran to “think very carefully” about any retaliation against Israel, western officials have told The National.
Mr Lammy spoke to Mr Kani on Tuesday as concerns deepen over a co-ordinated missile attack on Israel.
“The message from the foreign secretary was loud and clear to think very carefully about any retaliation that they are planning in relation to Israel,” the western official said. But the source admitted it was “regrettable” that it was “a question of when, not if” there would be an Iranian response.
Mr Kani was particularly angry on how Israel had conducted its operations in Gaza and “the reality of the situation, when it appears the Israelis have taken out the [Hamas] chief negotiator” on Iranian soil.
Mr Lammy urged for the Gaza peace negotiations to resume as soon as possible. The conversation was a “good call” with a diplomatic tone, although both politicians “to some extent disagreed at times”.
He has cancelled several important bilateral meetings to remain in London this week to deal with any emergency and to speak to interlocutors “sending the message to all sides about taking a breath and that now is the time for cool heads”, the official said.
With additional reporting by Thomas Harding
