Lebanon said an Israeli strike on Friday cut off the main international road to Syria, after Israel said Hezbollah was transporting weapons through the tiny Mediterranean country's principal land border crossing.
The strike, which Israel has not commented on, comes after 310,000 people, mostly Syrians, have in recent days fled the war pitting Israel and Hezbollah in Lebanon for relative safety in neighbouring Syria.
It follows an intense night of bombardment of Hezbollah's main bastion in the southern suburbs of Beirut, with a US and an Israeli news website saying Israel targeted the militant group's potential successor just a week after it killed its leader, Hassan Nasrallah.
The escalating assaults by Israel come as it weighs retaliation for Hezbollah backer Iran's missile attack.
President Joe Biden said on Thursday that the United States was "discussing" possible Israeli strikes on Iranian oil facilities.
Iran's supreme leader, Ayatollah Ali Khamenei, delivered a rare sermon on Friday, his first since his country's missile attack on Israel, and also the first since Israel launched its wave of strikes on Hezbollah strongholds.
Thousands of Iranians were gathered in the capital Tehran to catch a glimpse of the leader, with a photograph of Khamenei placed side by side with a picture of Nasrallah on the main stage.
Some carried the green and yellow flag of Hezbollah, while others carried the Palestinian flag.
In Lebanon, a source close to Hezbollah said Nasrallah had been given a temporary burial in a secret location until a public funeral could be held.
Nearly a year after Palestinian militant group Hamas launched the deadliest attack on Israel in its history on October 7, Israel announced it was shifting its focus to securing its border with Lebanon.
Hezbollah started launching low-intensity strikes on Israel last October, in support of its allies in Gaza, forcing 60,000 Israelis to flee their homes in the north of the country.
Israel's bombing in Lebanon has killed more than 1,000 people since the start of the escalation on September 23, according to the Lebanese health ministry, and forced hundreds of thousands to flee their homes in a country already mired in economic crisis.
The overnight strikes on the southern suburbs of Beirut, Hezbollah's main bastion, destroyed at least five buildings and left a huge crater in the road, an AFP photographer said.
A target of one of Israel's recent Beirut strikes was Hashem Safieddine, a potential successor to Hezbollah chief Nasrallah who was assassinated a week ago, US news site Axios said, citing three Israeli officials it did not identify.
Israeli news website Ynet also reported Safieddine had been the target, while the Israeli military told AFP it was looking into the reports.
On Thursday, the Israeli military said it had hit "targets belonging to Hezbollah's intelligence headquarters in Beirut".
Its Arabic-language spokesman Avichay Adraee accused Hezbollah of using the main international border crossing out of Lebanon into Syria to transport weapons.
Coastal Lebanon shares a border with Israel, with which Hezbollah is at war, and Syria.
Hezbollah has historically relied on Syria, with which it is allied, to transport arms and other equipment from its main backer Iran.
Masnaa, as it is known, is the main overland crossing out of the country, and the strike could leave thousands who are unable to fly out trapped.
In Beirut, 35-year-old displaced nurse Fatima Salah said residents were "scared for our children, and this war is going to be long".
Israel announced this week that its troops had started ground raids into parts of southern Lebanon, a stronghold of Hezbollah, after days of heavy bombardment of areas across the country where the group holds sway.
Israel told Lebanese people Thursday to "immediately" evacuate more than 20 villages and the city of Nabatiyeh.
Hezbollah said it fought off Israeli troops on the border and set off two explosive devices against advancing soldiers.
The militant group also said it kept up its rocket fire, with sirens warning of incoming fire blaring in northern Israel Friday.
Lebanon's health ministry said Friday that 37 people were killed and 151 wounded by Israeli strikes over the previous 24 hours.
The Israeli military said nine of its soldiers have been killed in combat in Lebanon.
Supreme leader Khamenei was delivering a sermon Friday, days after Iran launched its second-ever direct attack on its arch-foe Israel, in what it said was revenge for the killing of Nasrallah and other top figures.
Iranian Foreign Minister Abbas Araghchi meanwhile landed in Beirut for talks with Lebanese officials, Lebanon's official National News Agency reported.
Israeli Defence Minister Yoav Gallant warned that "those who attack the state of Israel, pay a heavy price".
Iran said it would step up its response if Israel counterattacked.
Israel intercepted most of the 200 missiles launched by Iran, though the attack has sparked fear in Israel of more violence to come. In the West Bank, a Palestinian was killed by shrapnel.
Rony Eli-Ya, 37, an Israeli on a pilgrimage to Ukraine's Uman, said it was "a miracle, not a single rocket killed a single Jew" in the attack.
With fears of further violence drawing in more countries in the region, US President Biden said that "we can avoid" all-out war in the Middle East, but that "there is a lot to do yet, a lot to do yet."
In the occupied West Bank, a source within the Palestinian security services told AFP that an air raid on the refugee camp of Tulkarem, which killed 18 people, was the deadliest in the territory since 2000.
The Israeli military said its strike in the northern West Bank killed Hamas leader Zahi Yaser Abd al-Razeq Oufi, who it accused of participating in numerous attacks.
Alaa Sroji, a social activist from the area, said an Israeli warplane "hit a cafeteria in a four-storey building".
Calls for restraint have multiplied but months of similar calls to halt fighting in Gaza failed to bring a ceasefire.
Hamas's October 7 attack on Israel resulted in the deaths of 1,205 people in Israel, mostly civilians, according to an AFP tally based on Israeli official figures that include hostages killed in captivity.
Israel's retaliatory offensive in Gaza has killed at least 41,788 people, the majority of them civilians, according to figures provided by the Hamas-run territory's health ministry. The United Nations has described the figures as reliable.
