The Israeli army said its troops were locked in fierce clashes in Lebanon after launching a ground offensive Tuesday, escalating the conflict after a week of air strikes that killed hundreds.
The ground assault came as Israel targeted south Beirut, Damascus and Gaza, despite international calls for restraint to avoid a regional conflagration.
Israeli Defence Minister Yoav Gallant warned the fight was far from over, even after a massive strike on Beirut killed Hezbollah chief Hassan Nasrallah on Friday. His death dealt a heavy blow to the Iran-backed group.
The Israeli military said its forces, backed by air strikes and artillery, carried out "targeted ground raids" on Hezbollah positions in settlements along the border.
It said the targets posed an "immediate threat" to northern Israeli communities and warned Lebanese civilians against driving in a southern zone along the border.
"Intense fighting is taking place in southern Lebanon," army spokesman Avichay Adraee said on Telegram. "For your personal safety, we ask you not to travel by vehicles from the north to the south of the Litani River."
The military had earlier declared a military zone on parts of its border with Lebanon. It said projectiles were fired from Lebanon into the northern Israeli towns of Avivim and Metula.
Hezbollah said it had twice targeted "a movement of enemy soldiers in Metula with artillery shells".
Lebanon's official National News Agency said an Israeli air strike Tuesday on Ain al-Helweh camp killed six people, including Hassan Maqdah, the son of Mounir Maqdah who heads the Lebanese branch of Palestinian group Fatah's armed wing, the Al-Aqsa Martyrs' Brigades.
It also reported Israeli shelling of border settlements, killing 10 people from the same family, including at least two children, in Daoudieh village.
Deadly strikes on Damascus
As Israel announced its ground raids, Syria's official news agency SANA said the country's air defence systems had intercepted three rounds of strikes in the Damascus area.
State television said anchor Safaa Ahmad was killed "in the Israeli aggression" on Damascus, while SANA reported three civilians killed and nine others wounded.
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There was no immediate comment from the Israeli military, which has carried out hundreds of strikes on Syria in recent years.
There was no immediate comment from Hezbollah following the Israeli army's announcement of the ground raids, but the group's al-Manar television reported the Israeli statement on its Telegram channel.
US Defense Secretary Lloyd Austin late Monday gave Washington's backing to Israel "dismantling attack infrastructure along the border".
Hezbollah previously said it is "ready if Israel decides to enter by land".
US news site Axios cited two Israeli officials saying the military incursion is "targeted and limited in time and scope and is not intended to occupy southern Lebanon".
Lebanon's national army, dwarfed by Hezbollah's military power, was "repositioning" troops farther from the border, a military official told AFP.
World leaders have urged de-escalation, with UN Secretary-General Antonio Guterres's spokesman Stephane Dujarric saying: "We do not want any sort of ground invasion."
Israel orders Beirut evacuations
Israeli strikes on Lebanon killed 95 people on Monday, the health ministry said.
On Monday evening, the Israeli military ordered people in three districts of southern Beirut to evacuate.
"You are located near interests and facilities belonging to the terrorist Hezbollah group... you must evacuate the buildings immediately," Adraee said.
Hezbollah began low-intensity strikes on Israeli troops a day after its Palestinian ally Hamas staged its unprecedented attack on Israel on October 7, which triggered Israel's devastating assault on the Gaza Strip.
Iran has said Nasrallah's killing would bring about Israel's "destruction", though the foreign ministry said Monday that Tehran would not deploy any fighters to confront Israel.
Austin warned on Monday of "serious consequences for Iran" if Tehran directly attacks Israel.
Following a deadly strike in central Beirut Monday, resident Kahier Bannout, 42, said it was "supposed to be a safe area -- not a war zone".
"Everyone is afraid."
Lebanon's Health Minister Firass Abiad said more than 1,000 people have been killed since September 17.
Lebanese Prime Minister Najib Mikati on Tuesday appealed to the United Nations and donor countries for aid for the displaced, whom he previously estimated could be as many as one million people.
Gaza strikes
In Gaza, the civil defence authority said Tuesday that Israeli bombardment on homes killed 12 people in the central Nuseirat refugee camp.
Seven others were killed in Israeli strikes on a school sheltering displaced people east of Gaza City.
A UN Satellite Centre assessment issued Monday said "two-thirds of the total structures in the Gaza Strip have sustained damage" in nearly a year of war.
Hamas's October 7 attack on Israel resulted in the deaths of 1,205 people, mostly civilians, according to an AFP tally based on Israeli official figures that include hostages killed in captivity.
Israel's retaliatory military offensive has killed at least 41,615 people in Gaza, most of them civilians, according to figures provided by the Hamas-run territory's health ministry. The UN has described the figures as reliable.