The group World Central Kitchen said it was pausing operations after the "targeted Israeli strike" on Monday killed Australian, British, Palestinian, Polish and US-Canadian staff.
AFP video footage showed the impact hole of a strike in the roof of one charred vehicle, perforating the group's logo, as the Israeli army said it was investigating the incident.
The White House was "heartbroken," US National Security Council spokesperson Adrienne Watson wrote on X, stressing that relief workers "must be protected as they deliver aid that is desperately needed."
The aid workers' deaths came as fighting raged in the Gaza war sparked by Hamas's October 7 attack in which fierce battles have left the largest hospital, Al-Shifa, in ruins with hundreds reported killed.
Middle East tensions have surged after Israel was also blamed for deadly air strikes Monday on the Iranian consulate building in Syria's capital that killed several top Revolutionary Guard generals.
Tehran — which backs Hamas and several other groups fighting Israel and its allies across the region — has vowed revenge against long-time arch foe Israel.
Israeli Prime Minister Benjamin Netanyahu has vowed to push on with the war to destroy Hamas, despite rising concern voiced by top ally Washington, and nightly mass street protests at home demanding he step down.
The United States said Monday that it had expressed concerns to Israel about its planned offensive in Gaza's crowded southern city of Rafah, and that Israel had pledged to "take these concerns into account."
The right-wing Israeli premier also vowed on Monday to ban broadcasts from Israel by the Qatar-based news channel Al Jazeera, which he labelled a "terrorist channel."
The broadcaster, several of whose journalists have been killed and wounded in the war, called his comments a "dangerous, ludicrous lie."
'Beyond catastrophic'
The bloodiest-ever Gaza war erupted with Hamas's October 7 attack, which resulted in about 1,160 deaths in Israel, mostly civilians, according to an AFP tally based on Israeli official figures.
Israel's retaliatory campaign has killed at least 32,845 people, mostly women and children, according to the health ministry in Hamas-run Gaza.
Palestinian militants also seized around 250 hostages. Israel believes about 130 remain in Gaza, including 34 presumed dead.
On Monday, the army pulled out of Gaza City's Al-Shifa Hospital after a two-week military operation that left much of the complex in ruins and bodies scattered on the dusty grounds.
Israel said its forces had killed 200 enemy fighters, while a spokesman for Gaza's civil defence agency said 300 people had been killed in and around the hospital.
Israeli military spokesman Daniel Hagari said there were "more terrorists in the hospital than patients or medical staff," with 900 suspects detained of whom over 500 were "definitely" militants.
During the war, Gaza has been under a tight blockade, with the United Nations accusing Israel of preventing humanitarian aid deliveries and warning of "catastrophic" hunger.
The UN Population Fund's head for Gaza, Dominic Allen, told AFP the situation was "beyond catastrophic" with gaunt and starving people searching for food, and medicine running desperately low.
Foreign governments have ramped up deliveries by air and sea, although UN agencies have said repeatedly that road convoys are the only way of supplying food in the volume needed.
'Heartbroken' by deaths
The group WCK has been working to unload food brought via a maritime corridor from EU member-state Cyprus.
The bodies of the aid workers killed were taken to a hospital mortuary in the central town of Deir al-Balah, an AFP photographer reported.
One of them was laid on a makeshift stretcher, wearing a top emblazoned with the WCK name and logo.
The group's CEO Erin Gore said "I am heartbroken and appalled that we — World Central Kitchen and the world — lost beautiful lives today because of a targeted attack by the IDF."
The aid group said the team was traveling in a "de-conflicted" area in a convoy of "two armoured cars branded with the WCK logo and a soft skin vehicle" at the time of the strike.
"Despite coordinating movements with the (Israeli army), the convoy was hit as it was leaving the Deir al-Balah warehouse, where the team had unloaded more than 100 tons of humanitarian food aid brought to Gaza on the maritime route," it said.
The Israeli military said it was "conducting a thorough review at the highest levels to understand the circumstances of this tragic incident," adding it had been "working closely with WCK."
Spain's Prime Minister Peddro Sanchez demanded Israel explain the "brutal" strike, and Polish Foreign Minister Radoslaw Sikorski asked the Israeli ambassador for "urgent explanations."
Australian Prime Minister Anthony Albanese also condemned the "completely unacceptable" attack.
Strike on Iran mission
The Gaza war has heightened fears of a wider regional conflagration, as Israel has exchanged fire with Iran-backed Hezbollah in Lebanon and violence has flared in Iraq, Syria and Yemen.
Those fears intensified with the strikes in Damascus in which 11 people were killed according to Britain-based monitoring group the Syrian Observatory for Human Rights.
Iran's Islamic Revolutionary Guard Corps said seven of its members were killed, including the Brigadiers General Mohammad Reza Zahedi and Mohammad Hadi Haji Rahimi.
Israel did not comment, but Iran's Foreign Minister Hossein Amir-Abdollahian blamed it as well as its ally the United States, saying that "the Americans must take responsibility."
The UN Security Council was to discuss the strike later Tuesday at a meeting requested by Damascus ally Moscow.
Iranian President Ebrahim Raisi vowed that the "inhuman, aggressive and despicable act ... will not go unanswered."
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