Israeli forces have raided al-Shifa Hospital, where thousands of Palestinians are sheltering, following days of heavy attacks in the area surrounding the complex in Gaza City.

Israel’s military said early on Wednesday morning that it was carrying out an “operation against Hamas in a specified area” at al-Shifa. Calling the assault a “targeted operation” on Gaza’s largest medical facility, it said the raid was based on Israeli and United States intelligence.

Israel accuses Hamas, the group that governs Gaza, of using the hospital as a base. Hamas rejects the claim. Israel has not produced evidence to back up its assertion.

Dozens of Israeli soldiers entered the facility while tanks were stationed in the yard of the medical complex, Al Jazeera’s Tareq Abu Azzoum said, reporting from Khan Younis on Wednesday. The raid “is considered to be very risky and dangerous as inside the hospital there are around 7,500 Palestinians including patients, doctors and displaced people,” he said.

Dr Munir al-Bursh, the general director of hospitals in the Gaza Strip, told Al Jazeera that Israeli forces searched the basement of al-Shifa and entered the surgical and emergency buildings within the complex.

Dr Ahmed El Mokhallalati, a surgeon inside the facility, reported heavy gunfire and explosions could be heard in the compound. “We saw the [Israeli] tanks and the bulldozers on the centre’s campus,” he told Al Jazeera.

About 700 patients remain at the hospital, including about 100 in critical condition, Mokhallalati reported. More than 1,000 medical staff are also trapped on site, but they are unable to treat patients due to a shortage of medicine and fuel.

Thousands of civilians displaced by Israel’s five-week bombardment of Gaza, which has killed more than 11,200 Palestinians, are also inside al-Shifa Hospital.

Mokhallalati described the fear that has taken hold among the thousands trapped in the facility. “We don’t know what they will do to us. We don’t know whether they will kill people or terrorise them. We know all the propaganda is lies, and they know as well as we do that there is nothing at al-Shifa medical centre.”

‘Barbaric crime’

The area around al-Shifa has been battered by multiple Israeli attacks for weeks. The Israeli government has issued warnings to evacuate the facility. However, Palestinian medical officials have rejected the order, saying they cannot leave their patients behind.

Amid the raid, Palestinian Authority Health Minister Dr Mai al-Kaila said, in a statement published by the Palestinian news agency Wafa, that Israeli forces “are committing a new crime against humanity, medical staff, and patients”.

The Palestinian government holds Israeli forces “responsible for the lives of the medical staff, patients, and displaced people in the al-Shifa complex,” she added.

Hamas said that it holds Israel and US President Joe Biden responsible for the implications of the raid, labelling it a “barbaric crime against a medical facility protected by the fourth Geneva Convention”.

“The Israeli occupation and everyone who colluded with it to kill children, patients and innocent civilians will be held accountable,” the group said in a statement.

The US said it “has information” that Hamas and the Palestinian Islamic Jihad use Gaza’s hospitals, including al-Shifa, “to conceal and support their military operations and to hold hostages”.

At the same time, Washington has continued to offer words of caution, Reuters reported.

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.”

Hamas has denied it uses Gaza’s hospitals as a base and has invited the United Nations to send independent investigators to verify that Israel’s claims are “falsehoods”.

Ardi Imseis, an international law expert at Queen’s University in Canada, said Israel carries the burden to “produce evidence” and prove its claim that the hospital has been used by Hamas as a base.

“The object of the attack is a civilian object. Until such time that the Israelis provide proof that it has been converted into a military object, the civilian nature of the object does not change,” he said.

Omar Shakir, the Israel and Palestine Director at Human Rights Watch, told Al Jazeera that “the Israeli government has put forward no evidence that would justify stripping hospitals of their special protections under international humanitarian law”.

Even if Israel’s justifications for attacking hospitals are taken at “face value,” Shakir said, “international humanitarian law only allows attacking hospitals if room is made for safe evacuation”.

He added: “The reality here is there is no safe place to go in Gaza.”