It has been nearly 10 months since Aviva Siegel was freed from captivity in Gaza, but her thoughts remain in the Palestinian territory where her husband Keith is still held by Hamas.

Siegel is one of a group of hostages released during a brief truce in the Israel-Hamas war last year who now pine for the loved ones they left behind -- and worry about what stalled truce talks mean for their fate.

"I'm still in Gaza, I haven't left yet," Siegel told AFP, describing her mental state.

Newly freed from an Israeli prison, Wael Masha rode atop friends' shoulders through the streets of his West Bank refugee camp before bursting into his home to kiss his mother's feet.

Less than a year later, those friends carried the 18-year-old's body through the same streets after Israeli forces killed him in an air strike, describing him as an armed militant who posed a threat to Israeli forces.

The UN agency for Palestinian refugees is bracing for a triple crisis as Israeli strikes on Lebanon add to the strain it is facing in Gaza and the West Bank, its chief told AFP on Tuesday.

UNRWA, founded in 1949, provides services, including education and healthcare, for Palestinian refugees in Gaza, the Israeli-occupied West Bank, Lebanon, Syria and Jordan.

World leaders lined up at the United Nations on Tuesday to call on Israel to refrain from a full-scale war in Lebanon, with the organization's chief warning the situation was on the "brink."

The UN General Assembly, the high point of the international diplomatic calendar, comes after Lebanese authorities said Israeli strikes had killed 558 people -- 50 of them children.

"Full-scale war is not in anyone's interest. Even though the situation has escalated, a diplomatic solution is still possible," US President Joe Biden said in his farewell address to the global body.

French President Emmanuel Macron on Tuesday pressed Iran's new president to use his influence to dial down soaring tensions in Lebanon, where Israel is striking Tehran-backed Hezbollah.

Macron met with Masoud Pezeshkian, a self-styled reformist in a cleric-run state which Israel sees as its archenemy, on the sidelines of the annual UN General Assembly as casualties mounted in Lebanon.

Macron "highlighted the responsibility of Iran to support a general de-escalation and use its influence with destabilizing actors," an Elysee statement said, in a clear reference to Hezbollah.

Hezbollah announced on Wednesday the death of a commander, hours after the Israeli army said it had killed him in a strike on Beirut's southern suburbs which Lebanese authorities said killed six people.

In a statement, the Iran-backed group announced the death of "commander Ibrahim Mohammed Kobeissi", who was "martyred on the road to Jerusalem", the phrase Hezbollah uses to refer to fighters killed by Israeli strikes.

Ali Berri never imagined it would take almost 14 hours to reach Beirut from his home in south Lebanon after he and his family decided to flee heavy Israeli air strikes.

It took "from 10:00 am until midnight -- the traffic was totally jammed", said Berri, 55, who fled with his wife, son and elderly neighbour from the Tyre area on Monday.

The trip would normally take a couple of hours at most.

"We hope that the war will ease so we can return to our homes because what me and my family went through yesterday is really war," he told AFP.

World leaders expressed alarm Tuesday over the prospect of a wider war after Lebanon suffered its deadliest day in two decades after Israeli air strikes on Hezbollah strongholds.

After nearly a year of cross-border fire since the Gaza war erupted, Israeli bombardment on Monday killed 558 people in Lebanon, including 50 children, according to the country's health ministry.

The toll, the highest since Israel and Iran-backed Hezbollah went to war in mid-2006, raised fears of an all-out conflict engulfing the Middle East.

- 'Nonstop nightmare': UN -

Tens of thousands of people have fled their homes in Lebanon as Israeli strikes pummelled the country, the UN said Tuesday, calling events "extremely alarming".

"We are gravely concerned about the serious escalation in the attacks that we saw yesterday," UN refugee agency spokesman Matthew Saltmarsh told reporters in Geneva.

"Tens of thousands of people were forced from their homes yesterday and overnight, and the numbers continue to grow," he said.

The relentless exchanges of fire between Israel and Lebanon's Hezbollah of recent days have stoked fears the longtime foes are moving inexorably towards all-out war, despite international appeals for restraint.

AFP correspondents in Jerusalem and Beirut talked to officials and analysts who told them what the opposing sides hope to achieve by ramping up their attacks and whether there is any way out.

- View from Israel -