"We have called on Israel to immediately investigate and provide a full, transparent explanation of what happened," Cameron said on social media, adding the UK was "urgently working to verify" details about the incident.

The US-based World Central Kitchen charity has blamed Israel for the strike Monday that killed seven of its staff unloading food brought by sea to the war-torn Gaza Strip to help alleviate looming famine.

The group has said it was pausing operations after the "targeted Israeli strike" killed Australian, British, Palestinian, Polish and US-Canadian staff.

The Israeli military has said it was "conducting a thorough review at the highest levels to understand the circumstances of this tragic incident".

In his first response, UK Prime Minister Rishi Sunak said he was "shocked and saddened" by the reported death of the British aid worker, adding "clearly there are questions that need to be answered".

Cameron, who was prime minister from 2010 to 2016 and returned to frontline politics last year as the UK's top diplomat, called news of the strike "deeply distressing".

"British Nationals are reported to have been killed, we are urgently working to verify this information and will provide full support to their families," he added.

"These were people who were working to deliver life-saving aid to those who desperately need it.

"It is essential that humanitarian workers are protected and able to carry out their work."

Cameron has become increasingly critical of aspects of Israel's war in Gaza since Hamas's October 7 attack, repeatedly calling for more aid to be allowed into the territory.