The Israeli military taking us deep into the heart of Gaza City. This is what much of Northern Gaza looks like as the Israeli military continues its mission to destroy Hamas. The roads ground into dust and everywhere in the city of over a million people, those apocalyptic scenes. In Northern Gaza, we embedded with the Israeli military to see the Children's Hospital they say was used as Hamas Command Center. We're now inside this armor fighting vehicle, and we are going towards the Rantiss Specialized Children's Hospital and has been evacuated. Hospitals have become the focus of international concerns as conditions there deteriorate. Israel saying Hamas and Palestinian Islamic Jihad have been using hospitals like Al-Shifa Hospital, Gaza's largest, and the tunnels beneath them to hold hostages and to wage war against the Israeli military. Now the Biden administration saying declassified US intelligence corroborates Israel's claims.

Hamas and PIJ members operate a command and control node from Al-Shifah Hospital in Gaza City. They have weapons stored there and are prepared to respond to an Israeli military operation against the facility.

A US official saying the assessment is based on a variety of sources but did not provide additional details. Doctors at Al-Shifah deny that. They say the hospital is no longer functioning and desperation is mounting. Without fuel for their generators, 39-24, and three premature babies were removed from their incubators. Three of those babies have died. A doctor telling ABC News the rest are alive and in good condition. But workers telling us they have had to use gardening tools, even their bare hands, to bury scores of decomposing bodies in a mass grave. The Rantisa hospital is just about a mile away from Al-Shifah. We unload outside the hospital into active fighting. There, we meet Israel's Chief military spokesman, Daniel Hagarie, a former naval commando, and just up the street, those tanks firing. I don't know if you can hear all that small arms fire in the background. We had a get down now. And Higari leading us inside to a children's safe room he says was used as a Hamas command center. Those AK-47s look pretty old and rusty. I mean, was this a crack force that was here?

No, some.

Of the.

Gear was operational gear, but also some of the.

Terrorists fled away. Farther into the basement, a separate section- We see here a chair. -hagari revealing that chair, and we pressed the Israeli military for evidence that hostages were held here. Hagarie, what makes you think that this was a spot where somebody was held hostage?

We're going to bring here a forensic team. The only reason I brought you in, and I'm taking a huge risk, tying hostages on a chair in his facility in a basement, fighting us for a hospital, using the children here in this hospital, a hospital children as a human shield.

This is Hamas. But the hospital's director tonight denying Israel's claims, saying the facility was used for displaced families, not hostages.

Hi, everyone. George Stephanopoulos here. Thanks for checking out the ABC News YouTube channel. If you'd like to get more videos, show highlights and watch live event coverage, click on the right over here to subscribe to our channel. And don't forget to download the ABC news app for breaking news alerts. Thanks for watching.