Israel has poured scorn on claims by the head of UNRWA that it was unaware of a subterranean Hamas facility built under the aid agency’s Gaza HQ.

Philippe Lazzarini, commissioner-general of UNRWA — which was set up to aid Palestinian refugees in 1949 following Israel’s War of Independence —tweeted that it “did not know what was under its headquarters” following revelations of the Hamas data centre by Israeli military officials.

But his claim of ignorance was immediately dismissed by Israel’s Co-ordinator of Government Activities in the Territories (COGAT) which tweeted back, “Oh, you knew”.

Several countries including the USA and UK have already frozen funds to UNWRA after allegations that a dozen of its staff took part in the October 7 massacre in Israel.

An Israeli document has also alleged that 12,000 of the agency’s officials have “close ties” with Hamas and Palestinian Islamic Jihad.

Israeli officials believe the underground data centre beneath the UNWRA HQ, which had computer servers and living quarters, was used by the terrorist group for intelligence gathering and communciations.

“There is no doubt that UNRWA staff knew that [Hamas] was digging a massive tunnel beneath them,” Colonel Benny Aharon, commander of the 401st Armoured Brigage, was quoted by the Times of Israel as saying “Whoever worked at UNRWA knew very well who was coming in, and who they were covering for.”

In his statement on X/Twitter on Saturday, Lazzarini said that UNWRA did “not have the military and security expertise nor the capacity to undertake military inspections of what is or might be under its premises.”

The building was vacated by UN staff on October 12 after Israel’s began its military operations following the Hamas assault.

He said the recent reports of the centre “merit an independent inquiry that is currently not possible to undertake given Gaza is an active war zone.”

The Israeli authorities had not informed UNWRA officially about the “alleged tunnel,” he added.

But in its counter-tweet, COGAT said, “Digging a tunnel takes longer than 4 months.

“We invited senior @UN officials to see, and during past meetings with you and other UN officials, we stated Hamas’s use of UNRWA's headquarters. You chose to ignore the facts so you can later try and deny them.”

Israel’s Foreign Minister Israel Katz has called for Lazzarini’s resignation.

Meanwhile, UK Foreign Secretary Lord Cameron has expressed concern over the prospect of an imminent Israeli attack on Rafah in the south of Gaza, saying the immediate priority should be a pause in the fighting.