Three Israeli soldiers were killed Wednesday when a tunnel opening they were investigating turned out to be booby-trapped. The tunnel opening was located under a United Nations Relief and Works Agency (UNRWA) clinic, the Times of Israel reports.

The deaths come a day after terrorist rockets were found inside a UNRWA school for the third time this month. The soldiers were in the clinic when the tunnel exploded and were killed when it collapsed. Another 15 soldiers were wounded.

Troops increasingly are encountering improvised explosive devices as they hunt for more Hamas tunnels, Brig. Gen. Micky Edelstein told the newspaper. In a briefing, IDF officials said they destroyed four more tunnels in the past day, and are "days away" from eliminating the tunnel threat.

Meanwhile, the UNRWA reported Tuesday that it found Hamas rockets in one of its Gaza schools for the third time since Israel's Operation Protective Edge began, the Times of Israel reports. The agency is devoted to helping Palestinian refugees, yet their premises are consistently exploited for the purposes of Hamas' terrorist operations.

"We condemn the group or groups who endangered civilians by placing these munitions in our school," said UNRWA Spokesperson Chris Gunness. "This is yet another flagrant violation of the neutrality of our premises. We call on all warring parties to respect the inviolability of UN property."

Hamas was not mentioned explicitly in the statement.

A week earlier, the U.N. agency discovered roughly 20 rockets in one of its school during an inspection. The first discovery of rockets in a UN center came July 16.

A UNRWA spokesperson stated that the organization gave the rockets to "local authorities," which answer to the Hamas-Palestinian Authority (PA) unity government led by PA President Mahmoud Abbas.

A senior Israeli official told the Times of Israel that the weapons were essentially returned to Hamas. "The rockets were passed onto the government authorities in Gaza, which is Hamas. In other words, UNRWA handed to Hamas rockets that could be shot at Israel."