PARIS, April 2, 2024 (BSS/AFP) - The United States, France and Britain led international criticism Tuesday of a deadly strike in the Gaza Strip that killed seven charity staff as they unloaded desperately needed aid brought by sea to the war-torn territory.

World Central Kitchen -- one of two NGOs spearheading efforts to deliver aid by boat -- said a "targeted Israeli strike" on Monday killed Australian, British, Palestinian, Polish and US-Canadian staff.

US Secretary of State Antony Blinken urged a "swift, impartial investigation" into the airstrike and said Israel needed to do more to protect innocent civilians.

Israel's Prime Minister Benjamin Netanyahu said the strike was "unintentional". The Israeli army has vowed to hold an investigation and promised to "share our findings transparently".

French Foreign Minister Stephane Sejourne, speaking alongside Blinken at a press conference in Paris, said "protecting humanitarian workers is a moral and legal imperative that everyone must adhere to. Nothing justifies such a tragedy."

Earlier, US National Security Council spokesperson Adrienne Watson wrote on X, formerly Twitter, that Washington, Israel's main ally, was "heartbroken and deeply troubled by the strike".

British Foreign Secretary David Cameron -- who has been increasingly critical of Israel's war in Gaza -- said the country had "called on Israel to immediately investigate and provide a full, transparent explanation of what happened".

UK Prime Minister Rishi Sunak said he was "shocked and saddened" after learning that a Briton was among those killed.

Australian Prime Minister Anthony Albanese slammed the "completely unacceptable" attack, and called it a "tragedy that should never have occurred".

He offered "sincere condolences" to the family of Australian volunteer Lalzawmi "Zomi" Frankcom, who was killed in the strike.

"She just wanted to help out through this charity. That says everything about the character of this young woman," Albanese said.

- 'Indiscriminate killing' -

The founder and leader of World Central Kitchen, Spanish-born US-based celebrity chef Jose Andres, said he was "heartbroken and grieving for their families and friends and our whole WCK family".

"The Israeli government needs to stop this indiscriminate killing," he wrote on social media. "It needs to stop restricting humanitarian aid, stop killing civilians and aid workers, and stop using food as a weapon."

The charity said it had coordinated its movements with the Israeli army and was travelling in vehicles branded with its logo.

It has paused its operations in Gaza.

Spanish Prime Minister Pedro Sanchez, who Tuesday was visiting a Palestinian refugee camp in Jordan, said "I expect and demand that the Israeli government clarify as soon as possible the circumstances of this brutal attack that has taken the lives of seven aid workers who were doing nothing but helping."

The EU's foreign policy chief Josep Borrell, who is also Spanish, said that "despite all the demands to protect civilians and humanitarian workers, we see new innocent casualties".

"I condemn the attack and urge an investigation," he wrote on X.

Warsaw said it had asked the Israeli ambassador for "urgent explanations" about the incident, which killed one Polish citizen, and offered "condolences to the family of our brave volunteer".

Polish Foreign Minister Radoslaw Sikorski said the country had also opened its own inquiry into the aid worker's death.

Criticism also came from Beijing, which said it was "shocked" by the strike.

Since Hamas's October 7 attacks triggered the war, Gaza has been under a near-complete blockade, with the United Nations accusing Israel of preventing deliveries of humanitarian aid.