A senior US politician said Israel had received an official warning from Egypt of a possible attack from Gaza three days before Hamas launched its deadly cross-border assault on Saturday. Michael McCaul, the chair of the US House foreign affairs committee, speaking after an intelligence briefing to senior members of Congress, said it was not clear at what level the warning was given. “We know that Egypt has warned the Israelis three days prior that an event like this could happen,” McCaul, a Republican, told reporters on Wednesday. “I don’t want to get too much into classified [details], but a warning was given. I think the question was at what level.” Israel was caught off-guard by Saturday’s surprise attack, when more than 1,500 Hamas fighters breached the Gaza border fence in a number of locations, killing over 1,200 Israeli civilians at a music festival, kibbutzim and other sites near the border. It took several hours before Israel’s military was able to respond on the ground. Earlier this week, the country’s prime minister, Benjamin Netanyahu, denied Israel had received any advance warning from Cairo, when reports first emerged that an alert had been passed on from the country’s intelligence services. Netanyahu said such claims were “fake news” in an address to the Israeli people on Monday. Earlier that day his office said “no early message came from Egypt” and denied that the prime minister had recently met with the head of Egyptian intelligence to discuss any such warning. That had followed the first reports of a warning from Egypt. An Egyptian official told the Associated Press that Egypt, which often serves as a mediator between Israel and Hamas, had spoken repeatedly with the Israelis about “something big”. The unnamed official claimed Israeli officials were focused on the West Bank and had played down the threat from Gaza. “We have warned them an explosion of the situation is coming, and very soon, and it would be big. But they underestimated such warnings,” said the official, who spoke on condition of anonymity. Cairo has not commented officially on suggestions that it may have offered an early warning to Israel. However, Egyptian media with close ties to intelligence services on Wednesday quoted senior security sources denying Israeli press reports that such a warning was issued. Despite the denials, McCaul appeared confident that some sort of warning was passed on, and indicated he had been told that attack planning may have been going on for as long as year – without Israel or its allies noticing. “We’re not quite sure how we missed it. We’re not quite sure how Israel missed it,” he told reporters, acknowledging that US and western intelligence had also failed to foresee an attack that has been described as the deadliest day for Jews since the Holocaust. Sir Alex Younger, a former head of MI6, said Hamas was likely to have been able to achieve surprise by “the complete abandonment of any electronic device or signature”, thereby evading electronic surveillance or signals intelligence. Speaking on BBC Radio 4’s The Today podcast, Younger said he believed one issue was a structural problem, Israel’s “overreliance on a set of technology systems” to defend itself, including sensors to detect hostile activity near its border with Gaza. “Technology is good at revealing capabilities and actions, it’s not good at revealing intentions,” he said. But the former spy chief, who stepped down in 2020, said Israel’s failure to pre-empt the attack also stemmed from a wider “failure of imagination” – and drew a parallel with the misjudgment in the run-up to the 9/11 attacks. “9/11 classically was that. The assumption was not that we were vulnerable to anything in terms of this type of attack. The assumption was that it essentially wasn’t possible,” Younger said. “And it is my assumption, therefore … that there will have been data breaking through which probably could have been interpreted differently and certainly would be, with hindsight, but people were just not looking at it in that way.” That thinking was reflected in the fact that, Younger said, Israel had deployed at least 70% of its military in the West Bank, “including units territorially dedicated to Gaza”. There was “a conscious decision” to switch significant force away from the south, he said. Israeli retaliatory strikes on Gaza have killed 1,100 Palestinians, including 326 children, with 5,339 people injured. More than 260,000 people have fled their homes in the Gaza Strip as heavy Israeli bombardments from the air, land and sea continued, the UN said. The former British spy chief also warned that Hamas was “essentially laying a trap for Israel and would be well pleased if Israel commits itself to a full-scale ground invasion of Gaza” – because of the intensity of fighting and the inevitable loss of civilian life that would follow. “You cannot kill all the terrorists without creating more terrorists,” he said.