Israel's military has released a video of what it claims is a 55-metre tunnel used by Hamas beneath Gaza's largest hospital.
The footage, purportedly filmed at al Shifa, begins with images of what is described as an "operational tunnel shaft", which looks like a circular hole in the ground.
The shaft is said to drop 10m, negotiated using a three-metre ladder and a spiral staircase for the other seven metres, the Israel Defence Forces (IDF) said.
At the bottom is a tunnel in two sections of five metres and 50m, the IDF added.
The shaft was uncovered after a controlled explosion was carried out on a vehicle the IDF said belonged to Hamas.
"The tunnel entrance contains various defence mechanisms, such as a blast-proof door and a firing hole, in an attempt by Hamas to block Israeli forces from entering," the IDF said on X, formerly known as Twitter.
"For weeks we've been telling the world about Hamas's cynical use of the residents of Gaza and patients of Shifa Hospital as human shields. Here is more proof."
There are blurry images of the "blast door" and its firing hole.
The tunnel itself has flat sides and a concave roof.
The video was filmed on Friday 17 November, according to a date stamp on the footage, and the tunnel has been investigated over the "last few days", said IDF spokesman Daniel Hagari.
He added: "The truth is clear. Hamas wages war from hospitals, wages terror from hospitals."
Sky News military analyst Sean Bell said robots had been used to access the tunnel, because it was a potentially dangerous environment for troops.
A tunnel is "not coherent with any form of normal hospital infrastructure", Bell said, adding that it appeared to be evidence that Hamas had been operating underground.
The IDF has said Hamas has a command centre beneath the hospital - a claim denied by Hamas and by hospital staff.
Richard Brennan, regional emergency director with the World Health Organisation, said the WHO was "very clear that any use of a medical facility for military purposes is a violation of international humanitarian law".
Earlier, the WHO said al Shifa hospital - previously the largest, most advanced and best-equipped hospital in Gaza - had essentially stopped functioning as a medical facility.
A team of UN and WHO experts conducted a "high-risk operation" on Saturday to get inside the hospital, despite heavy fighting reported to be ongoing nearby and a mass exodus of patients, doctors and other displaced people sheltering there.
A WHO spokesperson said: "Due to time limits associated with the security situation, the team was able to spend only one hour inside the hospital, which they described as a 'death zone' and the situation as 'desperate'.
"Signs of shelling and gunfire were evident. The team saw a mass grave at the entrance of the hospital and were told more than 80 people were buried there."
They said the facility had effectively stopped functioning as a hospital.