The IDF carried out a controlled explosion of a Hamas cross-border tunnel along the Gaza border Monday afternoon. According to Palestinian sources, the tunnel, built after the 2014 war with Gaza, crossed into Israel near the Palestinian city of Khan Yunis, in the southern Gaza Strip.

On the Israeli side, the tunnel terminated near the Israeli community of Kibbutz Kissufim. The IDF said that it was still under active construction at the time of demolition. The explosives were detonated from within Israel, near the security fence with Gaza, said a military statement.

“This is a severe violation of Israeli sovereignty and must not be overlooked,” an IDF spokesman said. “The successful operation was based on advanced technologies. The IDF continues [to combat tunnels] with the various means at its disposal which are becoming more and more sophisticated.”

While the tunnel was build by the Islamic Jihad terror group, the IDF emphasized that “the terror organization Hamas is responsible for everything that occurs in the Gaza Strip or emanates from there.”

According to media reports and the Gaza Health Ministry, seven people were killed and another 12 were injured by the blast on the Gazan side.

The operation followed an announcement Sunday by UNRWA, the United Nations agency tasked with aiding Palestinian refugees, which said it had found a tunnel under a school it operates in the Gaza Strip. UNRWA said the tunnel was discovered on October 15 and the school had been closed for 10 days, but it did not say where the tunnel had been found.

Israel’s Ambassador to the United Nations Danny Danon said the revelation of a tunnel under an UNRWA school yard showed “what Hamas rule looks like.”

Danon accused Hamas of  a “double war-crime committed as terror tunnels are built to attack Israelis, while using the children of Gaza as human shields.”

“We cannot accept a situation in which UNRWA schools are used as terror bases.  This dangerous incident must not be ignored and strict oversight is needed to ensure that UN facilities are not used to protect terrorists,” Danon said.