GAZA STRIP -- Israeli forces stormed Gaza's largest hospital Wednesday, targeting what they believe is a Hamas command center housed among thousands of ailing and sheltering civilians.

Israeli and Palestinian officials said military operations were taking place at Gaza City's Al-Shifa hospital -- the focal point of days of deadly fighting and nearby aerial bombardments.

Youssef Abul Reesh, an official from the Hamas-run Health inistry who is inside the hospital, told Agence France-Presse he could see tanks inside the complex and "dozens of soldiers and commandos inside the emergency and reception buildings."

The Israel Defense Forces described it as "a precise and targeted operation against Hamas in a specified area" of the facility.

After sharp warnings from the United States and others that Al-Shifa must be protected, Israel said the raid was being executed based on "an operational necessity."

Estimates for the number of patients, staff and displaced people inside the hospital complex range from the hundreds, to tens of thousands, with true number impossible to independently verify.

The White House reiterated its concerns for their safety, shortly after the raid began.

"We do not support striking a hospital from the air and we don't want to see a firefight in a hospital," a National Security Council spokesperson said.

The official added that there should not be a situation in which "innocent people, helpless people, sick people trying to get medical care they deserve are caught in the crossfire."

Earlier, the White House had said that US intelligence sources corroborated Israel's claim that Hamas and another Palestinian militant group, Islamic Jihad, has buried an operational "command and control node" under Al-Shifa.

Hamas, which has repeatedly denied the claims, on Wednesday accused US President Joe Biden of being "wholly responsible" for the Israeli assault.

Israel has also said that the military use of the hospital "jeopardises" its "protected status under international law," a claim that many international human rights lawyers refute.

Prime Minister Benjamin Netanyahu has vowed to destroy Hamas in response to its attacks on Oct. 7, which killed an estimated 1,200 people, mostly civilians, and saw 240 hostages being taken to Gaza.

Witnesses have described conditions inside the hospital as horrific, with medical procedures taking place without anesthetic, families with scant food or water living in corridors, and the stench of decomposing corpses filling the air. "There are bodies littered in the hospital complex and there is no longer electricity at the morgues," said hospital director Mohammad Abu Salmiya.

Anticipating a fierce backlash against the hospital raid, the Israel Defense Forces said it had provided evacuation routes for civilians and given authorities in Hamas-run Gaza 12 hours' notice that any military operation inside must cease.

"Unfortunately, it did not," the Israeli military said, again calling on "all Hamas terrorists present in the hospital to surrender."

The "intent" was that "no harm is caused to the civilians being used by Hamas as human shields," the Israeli military added.

Abul Reesh, from Gaza's Health Ministry, called on "the international community and the United Nations to intervene immediately and urgently to stop the Israeli storming operation." He urged both to protect what he said were "20,000 people inside the hospital including medical staff and 650 ailing people and thousands of injured people."

The situation in Gaza's other hospitals is also dire, with the UN saying 22 of 36 are not functional due to lack of generator fuel, damage and combat.

"The 14 hospitals remaining open have barely enough supplies to sustain critical and life-saving surgeries and provide inpatient care, including intensive care," the WHO said.

The UN "has warned that the evacuation of hospitals in the north, as demanded by the Israeli military, would be a 'death sentence' for some patients, because operational hospitals in the south cannot admit more patients," according to humanitarian agency OCHA.

The Health Ministry in Hamas-run Gaza says Israel's offensive has killed 11,320 people, mostly civilians, including thousands of children.

The humanitarian crisis in the territory also includes the hundreds of thousands of people who have fled southward.

Even escaping the fighting is dangerous. Wounded Palestinians told AFP how they were hit by a strike on their way south.

"I walked around 3 to 4 kilometers while I was bleeding," said Hasan Baker, whose head and left hand were bandaged. "There was no possibility for any ambulance to enter the area."

Israeli leaders have so far rejected any calls for a cease-fire in the five-week-old war until hostages are released. Abu Obeida, spokesman for Hamas' military wing, said Monday that Israel had asked for the release of 100 hostages, while the militants want 200 Palestinian children and 75 women freed from Israeli prisons.

"We informed the mediators we could release the hostages if we obtained five days of truce ... and passage of aid to all of our people throughout the Gaza Strip, but the enemy is procrastinating," Abu Obeida said in an audio statement.

Qatari Foreign Ministry spokesman Majed bin Mohammed Al-Ansari, who is helping oversee talks on a hostage deal, said the "deteriorating" situation in Gaza was hampering efforts to find agreement.

With pressure building on the Israeli government, Prime Minister Benjamin Netanyahu said he was "working relentlessly" to get the hostages out.

Relatives of the hostages set out Tuesday on a five-day protest march from Tel Aviv to the prime minister's office in Jerusalem to call for the captives' release, the Hostages and Missing Families Forum said.

The group later demanded the government "approve a deal tonight to bring home all hostages from Gaza."

US President Biden voiced confidence that a deal could still happen, telling the families of the hostages: "Hang in there. We're coming." (AFP-Yonhap)