A Palestinian-Irish doctor and senior plastic surgeon working at Al-Shifa Hospital in Gaza City has said that bombing in the hospital area was "continuous".
Speaking on RTÉ's News at One, Dr Ahmed El Mokhallalati said they are having "really very difficult times, scary times".
"Nothing would stop them (IDF) from getting in or doing whatever they want. They would kill everyone within the hospital," Dr El Mokhallalati said.
The World Health Organization said it was extremely worried for patients and staff at the hospital, which was stormed by Israeli troops overnight.
Israel's military said it carried out a targeted operation at the hospital, which it said may be the beating heart of Hamas, a claim the hospital and Hamas denies.
Spokesperson for the IDF Daniel Hagari said the operation was not intended to cause harm to civilians.
"Based on intelligence information and an operation of necessity, IDF forces are carrying out a precise and targeted operation against Hamas in a specified area in the Shifa hospital.
"Israel is at war with Hamas, not with the civilians in Gaza," he said.
Dr El Mokhallalati said that Israeli troops entered the hospital at 4am, he said tanks moved very close to the hospital and blocked two gates.
"And then they started really very aggressive bombing within Al-Shifa hospital.
"At 11 o'clock in the evening, we had direct bombing of the fourth floor of the main surgical building of Al-Shifa hospital. It came into the middle of one of the patient's rooms.
"There were four patients in that room, lucky enough they were not injured, so again, we were having really very difficult times, scary times."
Dr El Mokhallalati said inside the hospital, there is no electricity in the ICU department or the operating theatre and no water or oxygen supply.
"We are losing at least five patients every day from the ICU as we have no oxygen."
He said doctors are performing life-threatening cases only, but cannot offer general anesthesia as it requires oxygen.
"We had to do two cases. We have done them with light sedation, the patient was screaming, so we are not helping the patients, we are losing the patients in front of our eyes, they are slowly dying in front of us."
Dr El Mokhallalati said that while his pregnant wife and three young children are among the Irish citizens who are listed to leave Gaza today and enter Egypt through the Rafah crossing, they remain trapped in northern Gaza.
"It is impossible, Gaza is full of tanks.
"I can't move them to the south of Gaza because they can't go alone on their own. There are no cars. My wife has to walk for at least four kilometres, so it's a totally difficult situation for us," he said.
