The Israeli military took reporters on a tour of the tunnel. However, the lack of a mobile signal in the tunnel made it impossible to geolocate it and confirm it was indeed below the UNRWA headquarters, the Reuters news agency said.
"Everything is conducted from here. All the energy for the tunnels, which you walked through them are powered from here," Reuters cited a lieutenant-colonel, who gave only his first name, Ido, as saying during the tour.
He was referring to a side room in the tunnel packed with industrial battery stacks. Israel claimed the tunnel was powered by electricity supplied from the UNRWA headquarters.
UNRWA said its staff were forced to leave the headquarters on October 12, under Israeli instructions. It added that it had not used the facility since vacating and was not "aware of any activity that may have taken place there."
Gaza City, where the headquarters is based, was among the first regions of the enclave where Israel's ground offensive was focused.
The UN agency said it "does not have the military and security expertise nor the capacity to undertake military inspections of what is or might be under its premises."
UNRWA has come under fire in recent weeks after Israel alleged that members of its staff were involved in the deadly October 7 terror attacks, which Israel says left around 1,200 killed.
The agency fired 12 staff members and probed the allegations, but, in the process, many of its major donors have frozen their aid contributions, including Germany and the US.
