CAIRO -- Heavy Israeli bombardments pounded north and south Gaza on Monday, killing more civilians and once again bringing hospitals into the crossfire as the conflict entered its 45th day with few signs of letup.

Conditions were worsened by storms that dumped cold rain on the hundreds of thousands of displaced people who have been living in tents and makeshift shelters to try to escape the fighting.

In a rare moment of positive news amid the grinding conflict, more than two dozen very sick premature babies, 11 of them in critical condition, were evacuated from the Gaza Strip in ambulances to hospitals in Egypt.

The plight of babies trapped in al-Shifa Hospital, their lives threatened by the lack of food, water and electricity, had drawn global attention.

Hospitals have become a focal point of the fighting. Israel accuses Hamas fighters of using the buildings as strategic hubs and the residents inside as human shields. Hamas has denied the claims, and hospital directors and doctors from the Gaza Health Ministry have repeatedly called for international investigators to enter Gaza and search the buildings.

An Israel Defense Forces spokesperson said Monday that troops had found a Hamas weapons laboratory inside a mosque in the area.

"This is how we work. We discover and we reveal to the world what Hamas does, hiding its terror in mosques, schools and hospitals," Rear Adm. Daniel Hagari told reporters.

The Washington Post was not able to independently verify the account of a weapons laboratory in a mosque. Israel has repeatedly warned that Hamas militants use civilian buildings, including hospitals and places of worship, for military purposes. But it has provided limited access to the sites, which makes the claims hard to corroborate.

Hagari said IDF troops had been fighting the Zeitoun Brigade of Hamas's military wing, which operates in the Zeitoun area of northern Gaza City.

"Our forces located and destroyed many properties of the brigade, including laboratories to create missiles, weaponry, terrorist materials and intelligence materials," he said.

With al-Shifa, the Gaza Strip's largest hospital, largely evacuated, another medical facility in northern Gaza was on the firing line: The Indonesian Hospital, where many wounded were sent after al-Shifa ceased functioning.

The hospital's surgery department was struck early Monday, hospital director Marwan al-Sultan said. Ten patients who had been under anesthetic were killed. "The department is completely destroyed," he told The Post. "There is shrapnel everywhere. There is shooting targeting all windows around the hospital."

The Israel Defense Forces said militants had opened fire on its troops from within the hospital. "In response, IDF troops directly targeted the specific source of enemy fire. No shells were fired toward the hospital."

The Gaza Health Ministry said on its Telegram channel that 12 people were killed in the strike. Medical teams are refusing to leave while patients are there, the ministry said, even as attacks have intensified.

The hospital is hosting about 4,000 displaced people and has roughly 200 staff members, Sultan said. Of the 600 wounded who remain, he said, 150 are incapable of walking without assistance. They include men, women and children with fractures, lower limb amputations or orthopedic fixation devices.

"Patients and injured on their deathbeds are being targeted and they're dying from tank shelling, not their injuries," Mohammed Zaqout, director general of hospitals in Gaza, told Al Jazeera. He said machinery was destroyed and ceilings had collapsed atop the thousands holed up in the medical infrastructure. "Many have died," he said.

The Kamal Adwan Hospital was also targeted, Zaqout said, and was no longer able to provide even basic first aid to the hundreds of injured. As with other hospitals, the Israelis have contacted the facility and told it to evacuate.

"Of course they don't know where to evacuate to, with the presence of hundreds of injured. And there's effectively no hospital it can evacuate to," he said. "This is mass killing. This is extermination."

Doctors Without Borders said its clinic in Gaza City came under fire in the morning. Employees reported a wall torn down and a fire engulfing part of the building amid heavy fighting in the area.

"An Israeli tank was seen in the street," the organization, which goes by MSF, its initials in French, said in a statement. Four of its cars were burned, it said, and a fifth was broken in two, "as if crushed by a heavy-duty vehicle or a tank." All cars and the clinic were clearly identified with its logo.

"The cars destroyed are the same that were used to attempt the aborted evacuation of MSF staff and their families on" Saturday, the organization said. The evacuation failed when the convoy was fired on.

Heavy fighting continued to rage in pockets around the north. Israeli officials have indicated that they could soon expand the campaign against Hamas to other parts of the Gaza Strip.

Hamas and its allies launched a surprise attack on Israeli villages around Gaza on Oct. 7. They killed at least 1,200 people in Israel and took at least 240 more back to Gaza as hostages. In response, Israel has mounted a military campaign to dismantle Hamas rule in the enclave. More than 11,000 Palestinians in Gaza had been killed by Nov. 10, health officials there said, when communications prevented them from continuing to maintain an accurate count.

Much of the population of northern Gaza has made the long trek south, mostly by foot, along a road dotted with decomposing bodies and Israeli tanks. But the south, too, is suffering bombardment, and has overwhelmed hospitals and shelters, and dismal encampments.

Strikes began hitting residential neighborhoods in the southern city of Rafah early Monday and continued throughout the day. One airstrike killed 19 people from the same family, according to a doctor at Mohammed Yousef al-Najar Hospital.

"Medical staff are still here," the doctor said. "But sadly, with no electricity, power, gas nor water nor medical supplies, what can medical teams do?" He spoke on the condition of anonymity because he was not authorized to speak to the media.

When the bodies arrived at dawn, medical workers recognized two: a nurse and a technician who worked at the hospital. Also killed, the doctor said, were their parents, their children and a sister.

Around a dozen bodies arrived at al-Aqsa Hospital in the central Gaza Strip, a witness told The Post. They were victims of a strike that hit a school operated by the U.N. agency on Palestinian affairs not far from the border with Egypt. UNRWA, the agency, did not immediately confirm the attack.

In the south, the need for shelter was acute. One former medical worker at al-Shifa Hospital said he was staying in an UNRWA storage facility. As storms raged overnight, many who were sheltering in tents outside the warehouse lost them to the wind. There were "no blankets and yesterday there was wind and heavy rain," said the worker, who declined to give his name. "People had their tents flying off and submerged by water."

People were sleeping on thin carpets or old clothes. The bathrooms were not fit for humans, he said. The number of people was increasing daily.

At least 1.7 million people have been displaced in Gaza, according to the U.N. Office for the Coordination of Humanitarian Affairs, and overcrowding in shelters is contributing to disease. "On average, there is one shower unit for every 700 people and a single toilet for every 150 people," the agency said in a statement Sunday.

There isn't enough food to go around either, the medical worker said. Each family is given cheese and three tuna cans every couple of days, regardless of their numbers. "There is nothing," he said. "The shops have not had any goods reach them for almost two months."

News sometimes trickles in from al-Shifa. One colleague, a man who would jokingly ask his help in finding a wife, was killed in an airstrike. "He wanted the war to be over soon. He had just graduated and did not see much of the world, so it was truly killing him inside."