The World Health Organization (WHO) says Al-Shifa hospital in Gaza City "is not functioning as a hospital anymore".
The WHO says "constant gunfire and bombings in the area have exacerbated the already critical circumstances".
The BBC has been sent pictures of at least 20 newborn babies being kept in a surgical theatre at the site.
The Israeli military says it has agreed to help evacuate babies from the hospital to a "safer" facility but denies Al-Shifa has lost power.
Israel's president Isaac Herzog says Hamas has its base underneath the building - something Hamas denies. The Israeli military says it is not hitting the hospital during fighting.
Gaza's second biggest hospital, Al-Quds, is also reported by a charity to have run out of fuel.
Israel began striking Gaza after the Hamas attacks on 7 October, which saw 1,200 people killed and more than 200 taken hostage.
The Hamas-run health ministry says more than 11,000 people have been killed in Gaza since - of whom more than 4,500 were children.
Latest Stories
-
I want to focus more on my education – Chidimma Adetshina quits pageantry
2 hours -
Priest replaced after Sabrina Carpenter shoots music video in his church
2 hours -
Duct-taped banana artwork sells for $6.2m in NYC
2 hours -
Arrest warrants issued for Netanyahu, Gallant and Hamas commander over alleged war crimes
2 hours -
Actors Jonathan Majors and Meagan Good are engaged
2 hours -
Expired rice saga: A ‘best before date’ can be extended – Food and Agriculture Engineer
3 hours -
Why I rejected Range Rover gift from a man – Tiwa Savage
3 hours -
KNUST Engineering College honours Telecel Ghana CEO at Alumni Excellence Awards
3 hours -
Postecoglou backs Bentancur appeal after ‘mistake’
3 hours -
#Manifesto debate: NDC to enact and pass National Climate Law – Prof Klutse
3 hours -
‘Everything a manager could wish for’ – Guardiola signs new deal
4 hours -
TEWU suspends strike after NLC directive, urges swift resolution of grievances
4 hours -
Netflix debuts Grain Media’s explosive film
4 hours -
‘Expired’ rice scandal: FDA is complicit; top officials must be fired – Ablakwa
5 hours -
#TheManifestoDebate: We’ll provide potable water, expand water distribution network – NDC
5 hours