The Israeli military said Tuesday that it had begun pumping water into the vast network of tunnels beneath Gaza, which Hamas has used to launch attacks, store weapons and imprison Israeli hostages.

The military “has implemented new capabilities to neutralize underground terrorist infrastructure in the Gaza Strip by channeling large volumes of water into the tunnels,” the Israeli military said in a statement.

The statement was the military’s first public acknowledgment that its engineers were flooding tunnels, a contentious strategy that some military officials have said is ineffective and that the U.N. has warned could damage Gaza’s drinking water and sewage systems.

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