UN humanitarian chief Martin Griffiths said on Wednesday he was concerned that the Gaza war could spread across the region, including the West Bank, despite aid agencies being properly prepared for that eventuality.
The UN official warned that a spillover to Lebanon of Israel's war against Hamas in the Gaza Strip would be "potentially a scene of the apocalypse".
"I see this as the spark that will ignite the tension.
It could be an apocalypse," Martin Griffiths, whose term ends at the end of the month, warned reporters from Geneva.
The possible consequences are "unpredictable", he added.
A conflict involving Lebanon "will reach Syria... it will also reach other territories" in the region, he said.
"This will definitely have consequences in Gaza and will definitely have an impact on the West Bank," he said. "It's very disturbing."
The war in the Gaza Strip, which erupted after Hamas' unprecedented attack on Israel on October 7, has led to violent incidents on Israel's northern border with Lebanon, where there are almost daily exchanges of fire between Hezbollah, an ally of the Islamist movement. Palestinians and the Israeli army.