PARIS, April 3, 2024 (BSS/AFP) - World powers widely condemned an Israeli strike in the Gaza Strip that killed seven charity staff delivering desperately needed aid to the war-torn territory.

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

US President Joe Biden said he was "outraged and heartbroken".

In a strongly worded statement, he said Israel's investigation of the strike "must be swift, it must bring accountability, and its findings must be made public."

Biden added that the provision of humanitarian relief in the Palestinian territory has been difficult "because Israel has not done enough to protect aid workers trying to deliver desperately needed help to civilians."

The United Nations says the war has left almost 200 aid workers dead, including more than 175 members of the UN's staff.

UN Secretary-General Antonio Guterres called the strike "unconscionable" but added that it was "an inevitable result of the way the war is being conducted".

"It demonstrates yet again the urgent need for an immediate humanitarian ceasefire, the unconditional release of all hostages, and the expansion of humanitarian aid into Gaza," he said in a speech to the UN General Assembly.

Israel's army acknowledged on Wednesday it had committed a "grave mistake."

"It shouldn't have happened," IDF chief Herzi Halevi said in a video message, as he blamed the strike on a "misidentification -- at night during a war in very complex conditions".

Israeli President Isaac Herzog said he called WCK founder, chef Jose Andres, to express his "deep sorrow and sincere apologies over the tragic loss of life".

Prime Minister Benjamin Netanyahu said the strike was "unintentional" but stopped short of apologising for the deaths that he described as a "tragic case". The Israeli army has vowed to hold an investigation and promised to "share our findings transparently".

UK Prime Minister Rishi Sunak said he was "shocked and saddened" after learning that British nationals were among those killed.

He spoke to Netanyahu and told the Israeli leader that "he was appalled by the killing of aid workers", a Downing Street spokesperson said in a statement.

The UK summoned the Israeli ambassador to express its "unequivocal condemnation".

French Foreign Minister Stephane Sejourne said that "nothing justifies such a tragedy", adding that "protecting humanitarian workers is a moral and legal imperative that everyone must adhere to".

Australian Prime Minister Anthony Albanese slammed the "completely unacceptable" attack, called it a "tragedy that should never have occurred", and 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 chef 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 now paused its operations in Gaza.

Spanish Prime Minister Pedro Sanchez, who on 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".

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".

Warsaw said it 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 and Deputy Foreign Minister Andrzej Szejna said that Israel should compensate the families of the aid workers killed.

"The authorities should think about who should be held criminally responsible for pressing a certain button and how to compensate the families of the victims -- even if it's impossible to do so with money," Szejna told Radio Zet.

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.