The tunnel shaft, some two meters (6-1/2 feet) high, was accessed through an outdoor shaft in the hospital complex grounds, which were once crowded with tens of thousands of Palestinian civilians the army said had served as a human shield from war.

"That's the way that they survive because they use the hospital as a human shield that protects them," said Colonel Elad Tsuri, commander of an Israeli armoured brigade that found the tunnel. "And here they can stay for a long time. There is a room with air conditioning inside."

Israel has long accused Hamas of using the Shifa hospital complex as a command and control center as part of a wider strategy that seeks to hide its forces among the civilian population.

Hamas and hospital officials have denied the accusation and the hospital site has been at the centre of accusations of war crimes on both sides, with Palestinians accusing Israel of targeting hospitals and Israel saying the sites were being used to shelter armed fighters.

Journalists were driven in Israeli military vehicles to the hospital complex in the northern Gaza Strip past a landscape of buildings destroyed or vacated during Israel's nearly seven-week-old invasion of the Palestinian enclave.

Graced with arches, the tunnel was a well-built structure lined with stone and concrete. Army escorts used flashlights to illuminate the way in the dark and showed a small kitchen, a bathroom equipped with a toilet and sink behind a closed door, as well as a room large enough for meetings with two metal beds.

"We assume that there is another way out that they prepared. It's not open yet and we are sure that there are ways to the city from here," Tsuri said. He said the army knew the tunnel led to another opening in a Gaza kindergarten.

Israel has faced international criticism for its Gaza campaign, including its attacks on Shifa, the enclave's largest hospital. Medical officials say Israel has killed around 13,000 people in the strip since Hamas' Oct. 7 attack on Israel in which Israel says 1,200 people were killed and 240 taken hostage.

Outside on the ground, the army showed scores of guns, grenades and other explosives that military spokesperson Rear Admiral Daniel Hagari said had been collected in recent days inside the hospital, a motor home and nearby cars.

He said the body of one hostage, Noa Marciano, 19, had been recovered by the army outside a nearby medical clinic. Hamas earlier released a video saying she had died in an Israeli air strike. It was impossible to verify the claim.

In Washington, the White House has said its independent intelligence supported Israel's claim that Hamas was using Gaza's hospitals, including Shifa, to hide command posts.

Hamas responded at the time: "The White House and the Pentagon's adoption of the false (Israeli) narrative, claiming that the resistance is using Al Shifa medical complex for military purposes, was a green light for the occupation (Israel) to commit more massacres against civilians."

But Hagari, referring to Hamas' use of a hideout beneath the hospital, said: "The world now should say what happened in Shifa, what happened in the hospitals, is a war crime."