Aid agencies hope to evacuate roughly 140 patients stranded in Gaza’s Nasser hospital, a World Health Organisation official has said, as Palestinian authorities reported that Israeli troops withdrew from the complex and then stormed it again.

Medical teams had buried on the grounds of the hospital 13 patients who had died because the facility had no power or oxygen, Reuters quotes Gaza’s health ministry as saying.

The WHO and partners have so far carried out three evacuations from the hospital, the latest on Wednesday, transferring a total of 51 patients to southern Gaza, the UN agency’s Ayadil Saparbekov told a press briefing.

“The WHO will continue to try evacuation of those critically ill and critically wounded patients from the Nasser hospital to other hospitals in the south, including the field hospitals that have been established in Rafah,” Saparbekov said. “However it’s a very difficult and high-risk mission.”

The number of patients remaining in Nasser hospital had been changing by the hour as some people left to escape the fighting and others succumbed to their wounds, Saparbekov said.

Gaza’s health ministry had said in an earlier statement on Wednesday that 110 patients were waiting to be evacuated. It said eight patients at Nasser had died due to the lack of power and oxygen four days previously and that their bodies had begun to decompose, posing a risk to other patients.