The international food charity World Central Kitchen has called for an independent investigation into the Israeli strikes that killed seven of its aid workers in Gaza on Monday,as the US president, Joe Biden, and Israeli prime minister, Benjamin Netanyahu, were expected to discuss the attack on the phone.

WCK asked Australia, Canada, Poland, the US and the UK, whose citizens were killed, to join them in demanding “an independent, third-party’’ inquiry into the strikes.

“This was a military attack that involved multiple strikes and targeted three WCK vehicles,” WCK said in a statement. “All three vehicles were carrying civilians; they were marked as WCK vehicles; and their movements were in full compliance with Israeli authorities, who were aware of their itinerary, route, and humanitarian mission.

“An independent investigation is the only way to determine the truth of what happened, ensure transparency and accountability for those responsible, and prevent future attacks on humanitarian aid workers.”

WCK asked the Israeli government to retain all the necessary evidence, including communications, video and audio recordings of the fatal strikes on their convoy. The bodies of six foreign staff of WCK were repatriated from Gaza via Egypt on Wednesday, while the Palestinian employee was buried in Gaza.

The Australian prime minister, Anthony Albanese, said on Thursday that Israel’s explanation for the deaths was “not good enough” while a diplomatic crisis between Poland and Israel has erupted after Israel’s ambassador to Poland, Yacov Livne, pushed back at what he said were attempts by the “extreme right and left in Poland” to accuse Israel of “intentional murder”.

The Polish president, Andrzej Duda, on Thursday called the comment “outrageous” and described the ambassador as “the biggest problem for the state of Israel in relations with Poland”.

The foreign ministry said Livne was summoned to a meeting on Friday morning.

Biden and Netanyahu are expected to speak on Thursday in their first phone call since the strikes. Biden has led a chorus of international anger over the attack on the employees of the US-based WCK, who were distributing desperately needed food to a population on the verge of famine.

The Pentagon said the US secretary of defense, Lloyd Austin, had urged Israel to take concrete steps to protect aid workers and Palestinian civilians in Gaza “after repeated coordination failures” when he spoke with Israeli minister of defence, Yoav Gallant, on Wednesday. “Secretary Austin expressed his outrage at the Israeli strike on a World Central Kitchen humanitarian aid convoy,” the Pentagon said. It added that Austin had urged Gallant to conduct “a swift and transparent” investigation, to share the conclusions publicly, and to hold those responsible to account.

The US has provided crucial military aid and diplomatic support for Israel’s nearly six-month offensive, which was launched in response to Hamas’s 7 October attack. There is no indication that the US will withdraw aid over the WCK strike.

Israel said on Thursday that its military’s investigation into the killing of the seven aid workers could take weeks, while Shimon Friedman, a spokesperson for Cogat, the arm of the Israeli military responsible for civilian affairs in the Palestinian territories, told the BBC they “hope for [the investigation to report] in the next few days”.

The IDF chief of staff, Herzi Halevi, attributed the strike to “misidentification”, adding that it “was not carried out with the intention of harming WCK aid workers”, and was a mistake that should not have happened. The Australian prime minister, Anthony Albanese, said on Thursday that the Israeli explanations were “not good enough”.

The IDF said it had halted leave for all combat units on Thursday and heightened its air defence command to deal with a possible missile or drone attack from Iran, amid concern about Tehran’s response to the death of two Iranian generals and five military advisers in an Israeli airstrike on an Iranian diplomatic compound in Damascus earlier this week. Reuters and Tel Aviv residents reported on Thursday that GPS services had been disrupted, an apparent measure to ward off guided missiles. Iran has vowed revenge.

Since the war began, Netanyahu has faced intense domestic pressure from the families and supporters of the hostages still held in Gaza, and from a resurgent anti-government protest movement.

On Wednesday Benny Gantz, a Netanyahu rival and member of the war cabinet, called for snap parliamentary elections in September. “We must set a consensual date for the month of September, or if you prefer for the first anniversary of the war,” Gantz said.

The prime minister’s Likud party rejected the call, but it was welcomed by the leader of the US Senate, Chuck Schumer, who last month urged new elections in a strident criticism of Netanyahu’s handling of the conflict. “When a leading member of Israel’s war cabinet calls for early elections and over 70% of the Israeli population agrees according to a major poll, you know it’s the right thing to do,” Schumer wrote on X.

Early elections require the agreement of 61 elected officials, or the majority of deputies in the Knesset, where the Likud has the most seats but does not have a majority.

Likud said a national poll while Israel was at war “would inevitably lead to paralysis” and harm the military’s fight in Gaza.