In a statement, UNRWA spokesperson Christopher Gunness said that the tunnels were discovered during construction of an extension of one of the buildings during summer vacation, when the schools were empty. The tunnel had no entry or exit points within the school.
"UNRWA condemns the existence of such tunnels in the strongest possible terms," the statement read. "It is unacceptable that students and staff are placed at risk in such a way. The construction and presence of tunnels under UN premises are incompatible with the respect of privileges and immunities owed to the United Nations under applicable international law, which provides that UN premises shall be inviolable. The sanctity and neutrality of UN premises must be preserved at all times."
UNRWA said it protested "robustly" to Hamas and intends to seal the tunnel.
In Response, Israel's COGAT (Coordination of Government Activities in the Territories) posted on Facebook, quoting the Saudi Arabian newspaper Okaz, which wrote on Friday "Hamas is the one leading Gaza into humanitarian disaster in that it takes over and confiscates humanitarian aid and threatens the lives of residents as it digs tunnels under schools and hospitals in order to take advantage of residents as human shields."
Israel’s Ambassador to the United Nations Danny Danon reacted harshly to the revelation. “This tunnel verifies what we have always known, that the cruelty of Hamas knows no bounds as they use the children of Gaza as human shields. Instead of UN schools serving as centers of learning and education, Hamas has turned them into terror bases for attacks on Israel,” said Ambassador Danon.
Danon called on the Secretary General and the Security Council to intervene to ensure the implementation of strict oversight over the UN body. “The UN must act immediately to ensure that their structures and institutions are not being used to harbor the terror infrastructure of Hamas,” he concluded.
Despite its denunciation, UNRWA has long had a tangled relationship with Hamas. During 2014's Operation Protective Edge, Hamas weapons were repeatedly discovered stored in UNRWA's schools, as often as three times in a single week. And in April, UNRWA had to suspend one of its employees who was elected to Hamas leadership.
UNRWA, established by the UN General Assembly in 1949, exists expressly to provide aid to "Palestinian Refugees in Jordan, Lebanon, Syria, West Bank, and the Gaza Strip."
In response, Hamas said in a statement that it strongly condemns UNRWA’s claims regarding “the existence of a tunnel below one of the schools in central Gaza.”
Hamas sought clarification regarding the issue, who insisted that there are no resistance operations in the said location.
They also said that their polices are based on respect for UNRWA institutions, "vital infrastructure, and public institutions by distancing them from resistance operations."
Danielle Ziri and Adam Rasgon contributed to this report.