Rescue workers in the Syrian city of Aleppo say every hospital in rebel-held areas has now been taken out - after an escalation in violence from government forces.
At least 61 civilians have been killed in the last 24 hours, as more than 180 airstrikes have left survivors without access to medical supplies.
The International Development Secretary Priti Patel told ITV News it's a humanitarian catastrophe that must be stopped.
There had been a three week truce to allow for a "humanitarian pause", encouraging civilians and fighters to leave the city.
Elizabeth Hoff, the WHO representative in Syria, told Reuters a UN-led group of aid agencies based over the border in Turkey "confirmed today that all hospitals in eastern Aleppo are out of service".
Video report by ITV News Correspondent Angus Walker
International Development Secretary Priti Patel said: "This sickening act is part of a humanitarian catastrophe that will leave hundreds of thousands of innocent civilians already desperate for food without access to medical care."
East Aleppo’s hospitals have been hit by bombs in more than 30 separate attacks since the siege started in July, charity MSF said.