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

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."

The number of hostages being held by Hamas in Gaza is now believed to be 155, Israel Defense Forces said Sunday.

The number of hostages rose from 126 earlier Sunday, the IDF said. An undetermined number of Americans are believed to be among the hostages, according to U.S. officials.

The Senate will start working on a compressive aid package for Israel despite dysfunction in the House of Representatives, which remains without a speaker, Senate Majority Leader Chuck Schumer said Sunday.

"We’re not waiting for the House. We believe if the Senate acts in a strong bipartisan way, it may indeed improve the chances that the House, even with its current dysfunction, will act," Schumer told reporters in Tel Aviv.

Schumer led a bipartisan delegation of senators to Israel to meet with high-ranking government officials following the Oct. 7 deadly terror attacks by Hamas. On Sunday, Schumer and other members of the delegation were rushed into a bomb shelter in Tel Aviv to wait out a rocket attack, according to a social media post from the New York senator.

-ABC News' Davone Morales