Israel-Gaza updates: IDF preparing for 'wide range of offensive plans'

Fourteen staff members from the United Nations Agency for Palestine Refugees have been killed in airstrikes on the Gaza Strip, United Nations Relief and Works Agency Commissioner-General Philippe Lazzarini said during remarks from the UNRWA headquarters in Jerusalem on Sunday.

Most of the UNRWA's 13,000 staff members in the Gaza Strip have now been displaced or are "out of their homes," Lazzarini added.

Unless supplies are brought into Gaza, UNRWA and other international aid workers will not be able to continue humanitarian operations, Lazzarini said.

"As I speak with you, Gaza is running out of water and electricity," Lazzarini said.

At least 400,000 people who have been displaced in Gaza are currently sheltering in UNRWA schools and buildings, most of which have not been equipped as emergency shelters, Lazzarini said.

-ABC News' Ely Brown

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Biggest concerns for Doctors Without Borders during Israel-Hamas war

Doctors Without Borders spokesperson Gabriel Naumann says “We need to have the siege fully lifted so people can have access to food and electricity."

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The U.S. will soon have the capability to move thousands of American citizens and their families out of Israel by sea, two sources familiar with the planning told ABC News.

Those fleeing by sea will be taken to Cyprus aboard a cruise ship-like vessel set to depart from the northern Israeli port city of Haifa on Monday, the sources said.

Boarding is scheduled to begin at 8 a.m. local time on Monday, according to the U.S. State Department. Boarding will proceed in order of arrival as capacity permits.

Flight departures out of Israel’s Ben Gurion International Airport will also continue "on a rolling basis" on Monday and Tuesday, according to the State Department.

"Please go to Ben Gurion International Airport, Terminal 3, if you wish to depart Israel," the State Department instructed travelers in an advisory on Sunday. "U.S. Embassy personnel will be present to direct you and provide specific flight information. Be prepared to wait."

-ABC News' Mary Alice Parks and Shannon Crawford

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US Embassy scrambles to bring Americans home from Israel

Citizens will be evacuated by boat to Cyprus beginning Monday, in addition to charter flights.

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The number of U.S. citizens killed in the Hamas attack on Israel rose to 30 on Sunday, according to the U.S. State Department.

At least 13 American nationals are still missing, a State Department spokesperson said.

The death toll for Americans killed in Israel rose from 29 on Saturday.

"At this time, we can confirm the deaths of 30 U.S. citizens. We extend our deepest condolences to the victims and to the families of all those affected," the State Department spokesperson said. "At this time, we are also aware of 13 American nationals who are unaccounted for. State Department personnel have been in contact with their families.

"The U.S. government is working around the clock to determine their whereabouts and is working with the Israeli government on every aspect of the hostage crisis, including sharing intelligence and deploying experts from across the United States government to advise the Israeli government on hostage recovery efforts."

-ABC News' Shannon Crawford

With deaths mounting from Israeli airstrikes in Gaza, the head of the U.N. Relief and Work Agency said Sunday that Gaza is running out of body bags.

Philippe Lazzarini, the UNRWA commissioner-general, called a news conference Sunday to "raise the alarm" that as of Sunday he and his colleague are "no longer able to provide humanitarian assistance" in Gaza.

"In fact, Gaza is being strangled and it seems that the world right now has lost its humanity," Lazarrini said.

He said Gaza has no electricity and is running out of water fast.

He added that an "unprecedented humanitarian catastrophe is unfolding under our eyes" in Gaza.

"Thousands of people have been killed, including children and women.  Gaza is now even running out of body bags," said Lazarrini.

The government media office in Gaza said is now considering digging mass graves, according to Reuters.

Lazarrini said 14 staff members of his agency are among the dead.

"They were teachers, engineers, guards and psychologists, an engineer and a gynecologist," Lazzarini said. "Most of our 13,000 UNRWA staff in the Gaza Strip are now displaced or out of their homes."