At least 492 people have been killed in intense and wide-ranging Israeli air strikes targeting Hezbollah in Lebanon, the country’s health ministry says, in the deadliest day of conflict there in almost 20 years.
Thousands of families have also fled their homes as the Israeli military said it hit 1,300 Hezbollah targets in an operation to destroy infrastructure that the armed group had built up since the 2006 war.
Hezbollah, meanwhile, launched more than 200 rockets into northern Israel, according to the military. Paramedics said two people were injured by shrapnel.
World powers have been urging restraint as both sides appear to be spiralling closer towards all-out war. Lebanon's health ministry said 35 children and 58 women were among the dead, while 1,645 others had been wounded.
It did not report how many of the casualties were civilians or combatants.
Health Minister Firass Abiad said thousands of families had also been displaced by the strikes.
UN Secretary General António Guterres expressed alarm at the escalating situation and said he did not want Lebanon to “become another Gaza”.
EU foreign affairs chief Josep Borrell said the "escalation is extremely dangerous and worrying" ahead of a gathering of world leaders at the UN in New York, adding "we are almost in a full-fledged war".
President Joe Biden said the US was “working to de-escalate in a way that allows people to return home safely”, while the Pentagon announced it was sending “a small number” of additional troops to the Middle East "out of an abundance of caution".
Nearly a year of cross-border fighting between Israel and Hezbollah sparked by the war in Gaza has killed hundreds of people, most of them Hezbollah fighters, and displaced tens of thousands on both sides of the frontier.
Hezbollah has said it is acting in support of Hamas and will not stop until there is a ceasefire in Gaza. Both groups are backed by Iran and proscribed as terrorist organisations by Israel, the UK and other countries.
The Pentagon said it was sending “a small number” of additional US troops to the Middle East amid the growing crisis.
"In light of increased tension in the Middle East and out of an abundance of caution, we are sending a small number of additional US military personnel forward to augment our forces that are already in the region," said Pentagon spokesman Maj Gen Pat Ryder in a briefing with reporters.
He would not answer any follow-up questions on the specifics. Lebanese media said the first wave of Israeli air strikes began at around 06:30 local time (03:30 GMT) on Monday.
“It was horrifying, the missiles flew over our heads. We woke up to the sound of bombings, we didn’t expect this,” one woman said.
Dozens of towns, villages and open areas were targeted throughout the day in the districts of Sidon, Marjayoun, Nabatieh, Bint Jbeil, Tyre, Jezzine and Zahrani in southern Lebanon, as well as the Zahle, Baalbek and Hermel districts in the eastern Bekaa Valley, according to the state-run National News Agency (NNA).
In the evening, it reported that a building in the Bir al-Abed area of the southern suburbs of the capital, Beirut, was hit by several missiles.
Lebanese security sources said the strike targeted Hezbollah’s top commander in southern Lebanon, Ali Karaki, but that it was not clear whether he was killed. Hezbollah’s media office said Karaki was “fine” and had “moved to a safe place”.
From the south to Beirut, roads were congested as people desperately tried to leave amid the bombardment and after receiving audio and text messages from the Israeli military warning them to move away immediately from buildings where Hezbollah was storing weapons.
A family of four riding on a motorbike spoke to the BBC in Beirut during a brief stop on their way to the northern city of Tripoli. "What do you want us to say? We just had to flee," the father said anxiously.
Information Minister Ziad Makary said his ministry had received an Israeli phone call urging it to evacuate its building in Beirut. However, he insisted that it would not comply with what he called “a psychological war”.
Prime Minister Najib Mikati, meanwhile, told a cabinet meeting: “The continued Israeli aggression on Lebanon is a war of extermination in every sense of the word.”
“We are working as a government to stop this new Israeli war and to avoid descending into the unknown,” he added.