GAZA — Israel launched early Wednesday morning what it called a “targeted” military operation inside Gaza’s largest hospital Al-Shifa, where thousands of Palestinians are believed to be sheltering.

Conditions inside the hospital, which has run out of fuel and is no longer considered operational, have deteriorated rapidly in recent days amid intense fighting, with doctors warning of a “catastrophic” situation for patients, staff and displaced people still inside.

In a statement posted online, the Israel Defense Forces said it had begun “a precise and targeted operation against Hamas in a specified area in the Shifa Hospital.” It remains unknown how many troops have entered the hospital, but Israeli tanks could be seen inside the facility’s complex, a journalist at Al-Shifa told CNN.

“We can see them pointing the guns of the tanks toward the hospital. We are not sure whether soldiers are inside the hospital [buildings], but they are inside the complex with the tanks,” Khader Al Za’anoun, a reporter for the Palestinian news agency, Wafa, told CNN.

He said there were gunfire exchanges across the yard, and some of the windows in one of the buildings were out.

In its statement Wednesday, Israel again accused Hamas of continuing to use the large hospital complex for military purposes which, it said, “jeopardizes the hospital’s protected status under international law.”

Hamas and hospital officials have consistently rejected Israel’s claims that Hamas has built a command center under the hospital.

A doctor inside Al-Shifa told CNN they were given 30 minutes’ warning before the Israeli operation began.

“We were asked to stay clear of the windows and the balconies. We can hear the armored vehicles, they are very close to the entrance of the complex,” Dr. Khaled Abu Samra said.

Hundreds of staff and patients are still inside Al Shifa, according to the most recent reports from the hospital, along with several thousand who have sought shelter from Israel’s air and ground offensive.

A statement from Hamas blamed both Israel and the United States for the Israeli army raid on the hospital. By supporting what it called Israel’s “false narrative” – that Hamas was using Al-Shifa as a command and control base – it said the US had given Israel, “a green light ... to commit more massacres against civilians.”

Palestinian Authority (PA) Health Minister Mai al-Kaila has accused Israel of committing a "new crime against humanity, medical staff and patients” by carrying out a military operation inside the hospital.

"We hold the occupation forces fully responsible for the lives of the medical staff, patients and displaced people in Al-Shifa," she said on Wednesday in a statement published by the Palestinian news agency Wafa.

In the first comments from the White House on Israel's raid on Al-Shifa hospital, a spokesperson for the White House National Security Council said, "We do not support striking a hospital from the air and we don't want to see a firefight in a hospital where innocent people, helpless people, sick people trying to get medical care they deserve are caught in the crossfire."

They reiterated President Biden's comments earlier on Tuesday that hospitals and patients must be protected.

The US President Biden and Israeli PM Netanhayu had a phone call discussion, the BBC reported.

In a statement the White House said both leaders "discussed at length ongoing efforts to secure the release of hostages held by Hamas, including many children and a number of Americans".

On Tuesday, the White House and the Pentagon said that Hamas is storing weapons and operating a command center from the hospital.

International pressure on the Israeli government has hardened in recent days amid accounts of desperate circumstances at Gaza’s fuel-starved hospitals, and severe shortages of food and water.

United Nations Secretary General Antonio Guterres on Tuesday repeated his calls for a ceasefire in Gaza “in the name of humanity.”

Doctors and journalists have described catastrophic conditions inside Al-Shifa.

“There is no more water, food, milk for children and babies ... the situation in the hospital is catastrophic,” hospital director Mohammad Abu Salmiya told CNN on Monday.

Journalist Al Za’anoun said people inside the hospital “are starving, there is no food or drinkable water, we barely get tap water for one hour a day.”

He said dozens of corpses are set to be buried in a mass grave in the yard of the hospital complex, as relatives cannot leave to bury their loved ones.

“The scene is horrifying, the smell of the dead people is unbearable, most of the bodies are of women and children,” Al Za’anoun told CNN.

Abu Salmiya told Al Jazeera there are plans to bury more than 150 bodies, but he was worried the grave would not be large enough.

In recent days, 15 patients have died at Al-Shifa, among them six newborns, due to power outages and a shortage of medical supplies, according to the Palestinian Ministry of Health in Ramallah, which draws its figures from the Hamas-controlled territory.

Premature babies were taken out of failed incubators and wrapped in foil on Monday in a desperate bid to keep them alive after oxygen supplies ran out. Images showed several newborn babies placed together on a bed.

Egyptian health minister Khaled Abdel Ghaffar said Tuesday they are working to bring 36 newborns from Al-Shifa to Egypt, though such a transfer would be dangerous.

The Ministry of Health in Gaza welcomed any international observers to inspect the medical facilities at Al-Shifa Hospital, a spokesperson for the Hamas-controlled ministry said Wednesday.

“We are ready to receive any international institutions to vouch and confirm medical work at Al-Shifa Medical Complex,” Dr. Ashraf Al-Qudra said in a statement released three hours before the IDF announced its operation in Al-Shifa Hospital.

Al-Qudra appealed to the international community to intervene to stop the fighting, calling the situation in the Al-Shifa medical complex “critical" and calling for "urgent action to save the patients inside."

“There are 1,500 medical staff members and around 7,000 displaced people inside Al-Shifa Medical Complex. We appeal to all countries to take urgent action to save the patients inside,” he said.

Al-Qudra added that Israeli military vehicles have surrounded the hospital complex and that shelling in the vicinity was ongoing.

The World Health Organization has recorded at least 137 attacks on health facilities in Gaza, which it said resulted in 521 deaths and 686 injuries.

Other protected sites, like schools, civilian shelters, and United Nations facilities have already been damaged or destroyed in over a month of Israeli airstrikes. On Monday, the United Nations Relief and Works Agency for Palestine Refugee announced that over 100 UN staffers had been killed in Gaza since fighting began – the most in the United Nations' history. — Agencies