Israel said it has blocked a tunnel leading out of the Gaza Strip dug by the Palestinian enclave's Hamas rulers.
Israel's army said on Monday the militant group wanted to use "attack tunnels" to infiltrate fighters and abduct Israeli soldiers or civilians as bargaining chips in prisoner exchanges.
It said the tunnel had "two routes belonging to the Hamas terrorist organisation, dug from the northern Gaza Strip".
The Israeli military posted a video on Twitter in which it claimed to show the location of the tunnel.
Hamas said in response that "the Palestinian resistance has the right to use all means to enhance its capabilities against the arrogance and criminality" of Israel.
The tunnel had "crossed into Israeli territory", said Israel's Brig Gen Nimrod Aloni, the outgoing commander of the Gaza division.
It stopped short of an underground concrete barrier and therefore "did not pose a threat to Israeli communities in the area near the Gaza Strip".
The army said the tunnel was neutralised. It told AFP that it had been "partly filled with engineering materials".
"This left the tunnel sealed off, unreachable. Explosives were not used in the process," it said.
It comes after a three-day conflict between Israel and militants in Gaza ended with an Egyptian-brokered truce.
At least 49 Palestinians were killed in the violence, including 17 children and several fighters from the Islamic Jihad movement. In Israel, three people were wounded by shrapnel.
Groups in Gaza, a densely populated coastal territory home to 2.3 million people, have used tunnels since 2007 when Israel imposed a blockade in response to Hamas seizing power there.
Smugglers also established a network of tunnels on the border with Egypt to import everything from household goods to cars and weapons.
In recent years, Egypt has destroyed most of those tunnels.
In December, Israeli authorities announced that they had completed construction of a barrier along the Gaza border, described as an "iron wall" equipped with underground sensors, radars and cameras to counter threats.