The Israeli military said it was carrying out an operation against Palestinian Hamas militants in the Gaza Strip's Al Shifa Hospital on Wednesday and urged all members of the group in the hospital to surrender.

Less than an hour earlier, around 1 a.m. local time (2300 GMT), a Gaza health ministry spokesman said Israel had told officials in the enclave that it would raid the Shifa hospital complex "in the coming minutes."

Five weeks after Israel began its assault on Gaza, the fate of Al Shifa has become a focus of international alarm because of worsening conditions in the facility. The plight of Gazan civilians has prompted calls for a humanitarian ceasefire.

In a statement, the Israel Defence Forces (IDF) said: "Based on intelligence information and an operational necessity, IDF forces are carrying out a precise and targeted operation against Hamas in a specified area in the Shifa hospital."

The military added: "The IDF forces include medical teams and Arabic speakers, who have undergone specified training to prepare for this complex and sensitive environment, with the intent that no harm is caused to the civilians."

Israel has said that Hamas has a command centre underneath Al Shifa hospital, the biggest in Gaza, and uses the hospital and tunnels underneath to conceal military operations and to hold hostages. Hamas denies it.

The U.S. said on Tuesday that its own intelligence supported those conclusions.

Israeli forces have waged fierce street battles against Hamas fighters over the past 10 days before advancing into the centre of Gaza City and surrounding Al Shifa.

Israel has sworn to destroy Hamas in retaliation for the militants' cross-border assault into Israel on Oct 7. Israel says Hamas killed 1,200 people in the rampage and took more than 240 hostage.

DIRE CONDITIONS

Hamas says 650 patients and 5,000 to 7,000 other civilians are trapped inside Al Shifa hospital grounds, under constant fire from Israeli snipers and drones. Amid shortages of fuel, water and supplies, it says 40 patients have died in recent days.

Thirty-six babies are left from the neo-natal ward after three died. Without fuel for generators to power incubators, the babies were being kept as warm as possible, lined up eight to a bed.

Palestinians trapped in the hospital dug a mass grave on Tuesday to bury patients who died and no plan was in place to evacuate babies despite Israel announcing an offer to send portable incubators, Ashraf Al-Qidra, Gaza's health ministry spokesman, said.

Qidra said there were about 100 bodies decomposing inside and no way to get them out.

U.N. Secretary-General Antonio Guterres was deeply disturbed by the "dramatic loss of life" in the hospitals, his spokesman said. "In the name of humanity, the secretary-general calls for an immediate humanitarian ceasefire," the spokesman told reporters.

Medical officials in Hamas-run Gaza say more than 11,000 people are confirmed dead from Israeli strikes, around 40% of them children, and countless others trapped under rubble.

Around two-thirds of Gaza's 2.3 million people have been made homeless, unable to escape the territory where food, fuel, fresh water and medical supplies are running out.