Israel Defense Forces troops exposed a 180-foot tunnel 32 feet deep underneath the Shifa Hospital, the IDF and Israel Securities Authority (ISA) said in a joint statement Sunday.

"A deep staircase leads to the entrance of the tunnel shaft, which consists of various defense means including a blast-proof door and a firing hole," the statement continues. "This type of door is used by the Hamas terrorist organization to block Israeli forces from entering the command centers and the underground assets belonging to Hamas. The tunnel shaft was uncovered in the area of the hospital underneath a shed alongside a vehicle containing numerous weapons including RPGs, explosives and Kalashnikov rifles.

"IDF and ISA forces are continuing to uncover the route of the tunnel," the statement adds.

The IDF said it expects to find more tunnels and underground facilities, and that the operation is ongoing and will take some time. About 300 people remain in the hospital, according to the IDF.

-ABC News' Yael Benaya

The World Health Organization confirmed earlier claims by the Palestinian Health Ministry that 31 "very sick" babies were safely transported from Al-Shifa Hospital to another hospital in southern Gaza on Sunday.

The premature infants were evacuated to the Emirates Hospital in Rafah, WHO officials said.

The babies were "clinging to life," the United Nations International Children's Emergency Fund (UNICEF) said in a statement, and their "condition was rapidly deteriorating."

The babies are expected to be transferred to another hospital in Egypt, said Dr. Ashraf al Qwadwa, a spokesperson for the Palestinian Health Ministry. He said nine premature babies have died since the start of a fuel crisis in Gaza prompted by the ongoing conflict.

Six health workers at the Al Shifa Hospital and 10 family members of staff there were also evacuated on Sunday along with the babies, according to the WHO statement, adding that further missions are planned to "urgently transport" the remaining patients and health staff out of the hospital.

-ABC News' Nasser Atta

A British-owned cargo ship operated by a Japanese company was hijacked by Houthi militants near Yemen in the southern Red Sea, officials said Sunday.

The Israel Defense Forces released a statement describing the hijacking as a "very grave incident of global consequence."

"The ship departed Turkey on its way to India, staffed by civilians of various nationalities, not including Israelis," the IDF said. "It is not an Israeli ship."

Israeli Prime Minister Benjamin Netanyahu's office called the incident an "Iranian attack on an international ship," adding the vessel was "hijacked on [an] Iranian whim by the Houthi militia in Yemen."

Netanyahu's office confirmed that no Israelis were on the ship, saying the 25-person crew was of different nationalities, including Ukrainians, Bulgarians, Filipinos and Mexicans.

The Houthi militant group is expected to hold a news conference, a spokesperson for the group said.

A spokesman for Yemen's Iran-aligned Houthi military, Yahya Sarea, had said earlier Sunday the group would target all ships owned or operated by Israeli companies or carrying the Israeli flag, according to the group's Telegram channel.

-ABC News' Nasser Atta, Jordana Miller and Dana Savir

Negotiations to free the more than 200 hostages believed to be held by Hamas in Gaza have "reached a very sensitive stage" as some of the key areas of disagreement have "narrowed," a top White House official told ABC's "This Week" on Sunday.

Jon Finer, deputy national security adviser to the White House, suggested that a breakthrough in the negotiations could be imminent.

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Some ‘gaps’ have ‘narrowed’ in Israel-Hamas talks: Jon Finer

"These talks have clearly reached a very sensitive stage," Finer told "This Week" co-anchor Martha Raddatz. "We’re following this minute by minute, hour by hour, and have been over a number of weeks. And this is an incredibly high priority for all of us in this administration up to and including, certainly, the president."

Amid new reporting by The Washington Post that an agreement is on the verge of being struck for dozens of captives to be released in exchange for a pause in the fighting, Finer said progress was being made but cautioned that the work was not done.

-ABC News' Tal Axelrod

At least three premature babies have died at the Al-Shifa Hospital in the Gaza Strip when a missile struck nearby and shut down the medical facility's backup generator, according to a doctor working at the hospital.

Dr. Ahmed Mokhallalti, the chief plastic surgeon at the hospital, told ABC News that the babies died when the power to their incubators was cut off Friday night into Saturday morning.

Mokhallalti said all of the hospital's ventilators were back up and running Sunday, but he expressed fear that more people would die at the hospital due to the relentless bombing.

Hospital officials said two patients in the hospital's intensive care unit also died on Sunday due to complications caused by the shelling.

The international humanitarian group Doctors Without Borders has made repeated calls for the shelling of hospitals in Gaza to cease.

"We are nearly sure that we are alone now. No one hears us," Dr. Mohammed Obeid of Doctors Without Borders said in a video statement from the Al-Shifa Hospital on Saturday.

Obeid said there are about 600 patients at the hospital who need medical care and need to be evacuated.

"The problem is [we need] to be sure we can evacuate the neonatal patients because we have 37 to 40 premature babies," Obeid said. "We have about 17 other patients in the ICU, and we have 600 postoperative patients who need medical care. So the situation is very bad. We need help."

-ABC News' Zoe Magee, Matt Gutman and Sami Zayara