The director of the Gaza Strip's main hospital raided by Israeli soldiers says the facility has now run out of oxygen and water, and patients "are screaming from thirst".
Muhammad Abu Salmiya said "the conditions are tragic" in Al-Shifa, where there were currently more than 650 patients, 500 medical staff and over 5,000 displaced people.
He also said Israeli tanks were surrounding the hospital, drones were buzzing overhead and Israeli soldiers were still moving around inside, as their search of the complex lasted a second day.
Israel's army said its operation against Hamas was proceeding in a "discreet, methodical and thorough manner". However a journalist trapped inside the hospital, Khader, told the BBC's Rushdi Abu Alouf by phone that Israeli troops were "everywhere, shooting in all directions".
The BBC has not been able to independently verify either of the reports.
The Israel Defense Forces (IDF) launched its raid on Al-Shifa in Gaza City early on Wednesday. It has released several photos and videos of what it says are Hamas weapons and equipment.
In a statement on Thursday, Mr Abu Salmiya said Israeli troops had blown up Al-Shifa's main water line.
"Sniping operations continue, no-one can move from one building to another, and we have lost communication with our colleagues," he said.
Earlier on Thursday, Khader told the BBC that Israeli troops had "stormed all departments", destroying the southern part of the building's wall and dozens of cars.
Before Khader's phone line cut off, he also said that armoured bulldozers had been brought in.
Gaza's Hamas-controlled health ministry also reported that Israeli bulldozers had "destroyed parts of the southern entrance" of the medical complex.
Israel launched a major military campaign in the Gaza Strip to destroy Hamas, which it considers a terrorist group, in retaliation for the 7 October cross-border attack by hundreds of gunmen. At least 1,200 people were killed in Hamas's assault on Israel and about 240 others were taken hostage.
Since Israel started its counter-attack, Gaza's Hamas-run health ministry has said 11,400 people have been killed in the territory and the United Nations has warned of a "humanitarian disaster".
On Thursday evening, the IDF announced that the body of one of the hostages had been found near Al-Shifa.
The IDF identified the victim as Yehudit Weiss, saying she had been kidnapped from her home in Be'eri - a kibbutz in southern Israel.
At the same time, there have been reports of a major phone and internet outage in Gaza believed to have been caused by telecom companies running out of fuel supplies.
The IDF said its soldiers were continuing its "complex and ongoing" operation against Hamas at the hospital.
"Soldiers are proceeding one building at a time, searching each floor, all while hundreds of patients and medical staff remain in the complex," an official said in an update on Thursday evening.
The official reiterated the IDF's claim that there was a "well-hidden terrorist infrastructure in the complex".
On Wednesday, it shared photos and videos that the IDF said were of Hamas weapons and equipment at the hospital, and on Thursday it said it had also found "an operational tunnel shaft and a vehicle containing a large number of weapons".
Hamas has repeatedly denied that its fighters were operating inside the hospital.
On Thursday, Osama Hamdan, the most senior Hamas leader in Lebanon, ridiculed the Israeli weapons claims, saying that all the arms had been brought in and planted in the hospital by Israelis.
Asked by the BBC why progress on talks to release hostages had failed, he said that on three occasion they had been close to a deal - but each time it had been stopped by Israeli Prime Minister Benjamin Netanyahu.
The Israeli government has not commented on Mr Hamdan's claim.
Israel's Army Radio on Wednesday reported that troops had not yet found any sign of any of the 240 hostages taken by Hamas during the 7 October attack on Israel, when 1,200 other people were killed.
In a separate development, Israel has dropped dropped leaflets in the Khan Younis area of southern Gaza, warning people in four towns to evacuate their homes and head to shelters.
If that is an indication of an upcoming military operation around the southern city of Khan Younis, it could be a real concern to the hundreds of thousands now sheltering there.
Before the war, Khan Younis was home to about 300,000 people - a number that has now grown to one million after Israel urged civilians to move south for their safety.
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