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A number of Israeli civilians were wounded when anti-tank guided missiles and rockets from Lebanon hit areas in Israel, including a convoy near an army barracks in the Dovev region, the Israeli military said on Sunday afternoon.
Hezbollah claimed responsibility for the two attacks on Dovev.
Meanwhile, Hamas's armed wing, the Ezzedine Al Qassam Brigades, claimed “several concentrated rocket volleys” fired from Lebanon deep into northern Israel reached the Krayot area north of Haifa and near the towns of Shlomi and Nahariyya.
It was a major escalation that prompted the Israeli army to threaten a "change in the security situation in the north", just one day after Hezbollah leader Hassan Nasrallah said the border area would “remain a front of pressure” to "stop the aggression on Gaza".
The intensified clashes continued throughout the day. At least 14 Israelis – soldiers and civilians – were injured in the attacks from Lebanon.
Typically, the Israeli army does not provide numbers for Israeli injuries or deaths.
By Saturday evening, Israeli media was reporting inconsistent numbers of wounded Israeli civilians and soldiers: between 18 and 23.
The significant progression of hostilities on the Lebanon-Israel border on Sunday prompted Israeli army spokesman Admiral Daniel Hagari to say that Israel will “change the security situation in the north”.
“The security situation will not remain in a way where residents of the north will not feel safe to return to their homes,” Admiral Hagari said.
He said Hezbollah and the Lebanese government would bear responsibility for the attacks.
“Lebanese citizens will pay the price of this lawlessness and the decision of Hezbollah to be the protector of ISIS," Admiral Hagari said, deliberately confusing Hamas with the extremist group.
Israel's ambulance service said at least six people had been wounded in the first attack on Dovev, one critically, while five others remained in serious condition.
Among the casualties were employees of the Israel Electric Corporation who were carrying out repairs in the area, Israeli newspaper Haaretz reported.
Hezbollah said it had attacked an Israeli logistics team trying to install new cameras and intelligence hardware.
Hezbollah also claimed another attack on Dovev, on the town’s army barracks, saying it was aiming at a bulldozer belonging to the Israeli military with guided missiles.
According to the Lebanese party’s statement, the driver of the bulldozer was killed and soldiers near by were also killed or injured. The Israeli army did not comment on the incident.
The Israeli army said it was retaliating with artillery fire on the "source of the launch" in the outskirts of Yaroun village in south Lebanon.
Meanwhile, the UN Interim Force in Lebanon, or Unifil, said one of its peacekeepers was injured after being hit by gunfire overnight.
It was unclear whether the gunfire came from Israeli or Lebanese parties.
"Shortly after midnight, peacekeepers at a Unifil site near Al Quzah reported that they heard gunfire nearby. One of the peacekeepers was hit by a bullet and underwent surgery," said Andrea Tenenti, Unifil spokesman.
Mr Tenenti told The National the origin of the bullet was "unknown" and the peacekeeper's condition was stable. He said Unifil was investigating.
Daily clashes have intensified between Lebanon's Hezbollah and Israel in the past month, coming to a head after Mr Nasrallah’s address.
Over a month of violence has claimed at least 90 lives on the Lebanese side, with 72 Hezbollah fighters and at least eight civilians among the dead.
Members of armed Palestinian groups operating from Lebanon were also among the casualties.
The Israeli army told The National that eight of its soldiers have been killed on the Lebanon-Israel front since the fighting began.
It declined to provide numbers for civilian casualties.
Hezbollah on Saturday claimed responsibility for an attack on eight military sites across the border in Israel, using artillery, anti-tank guided missiles and rockets.
Meanwhile, the Israeli army on Saturday said it had hit several Hezbollah sites in Lebanon with air strikes and artillery shelling.
In one instance on Saturday, Israel struck 40km over the border, hitting a banana plantation in the southern village of Zahrani, between Tyre and Saida.
It was Israel's deepest reach into Lebanon since the frontier conflict began on October 8.
The Amal Movement, the Lebanese political party allied with Hezbollah, said one of its fighters was killed and three injured in one of Israel’s attacks. It is the first death for Amal since the fighting began.
After Mr Nasrallah’s speech, Israeli Defence Minister Yoav Gallant warned residents of Beirut would pay the price if Israel was dragged into war with Hezbollah.
“What we are doing in Gaza we know how to do in Beirut,” he threatened during a visit to the border region.
“I am saying here to the citizens of Lebanon, I already see the citizens in Gaza walking with white flags along the coast and moving south."
Hezbollah has conducted or provided armed groups with cover for daily attacks on Israel’s northern border with Lebanon, seeking to draw Israel from focusing its full attention on the bombardment of the blockaded Gaza Strip.
But the Iran-backed group has not launched a full-scale campaign, despite escalating tensions at the border.
Armed Iran-allied groups in Syria, Yemen and Iraq have also attacked Israel, seeking to divert its assault on Gaza.
Israel has tempered its responses in an attempt to prevent a full-scale confrontation from breaking out and turning into a regional war.
In a long-awaited speech on November 3, Mr Nasrallah ruled out an all-out conflict in Lebanon, calling for a ceasefire.
But violence in the south has intensified, killing civilians, including three schoolgirls and their grandmother in an Israeli air strike last week.
On the same day, an anti-tank guided missile launched by Hezbollah killed an Israeli civilian.