At least 600 people in Israel have been killed in the surprise attacks by Hamas and at least 370 have been killed in retaliatory strikes in Gaza, Israeli and Palestinian health officials said Sunday.

At least 2,156 people have been injured in Israel, according to the Israeli Health Ministry. At least, 2,200 have been injured in Gaza, the Palestinian Health Authority said.

-ABC News' Joseph Simonetti

Republican presidential candidate Chris Christie slammed the dysfunctionin> the U.S. House of Representatives, where a small group of Republican lawmakers last week voted along with the Democratic minority to oust Speaker Kevin McCarthy, for leaving it without a way to pass legislation, including foreign aid to Israel.

"What I would be doing is making sure, one, that Israel has everything that it needs to be able to take whatever actions it needs to take. And this is the problem with not having a speaker right now," Christie, the former New Jersey governor, told ABC News' "This Week" anchor George Stephanopoulos.

Christie, a former ABC News contributor, added, "The actions taken by some members of my party were wholly irresponsible without this going on. They're now even putting a brighter light on the irresponsibility of not having someone in place."

Christie also said his top priorities if he were president would be engaging allies in the region, such as Jordan and Saudi Arabia, to keep the conflict from spreading and to serve as a "sounding board" to Israeli Prime Minister Benjamin Netanyahu to help him "think through the ramifications of every step they're going to take to defend themselves and to try to do the best they can to eliminate the leadership of Hamas."

-ABC Nicholas Kerr

For the first time since Saturday's surprise attack by Hamas militants, the Israeli government confirmed that a number of people, including civilians, have been taken hostage.

Israel's Government Press Office said Sunday that at least 100 Israeli citizens and soldiers are being held hostage by Hamas fighters.

U.S. Secretary of State Antony Blinken said in separate interviews on CNN and NBC News that there is a possibility Americans are among those killed or taken hostage and that the U.S. Department of State is investigating.

-ABC News' Joe Simonetti

Secretary of State Antony Blinken on Sunday pushed back on growing Republican criticism that the White House's decision to allow the transfer of some $6 billion of Iran's oil revenue, in exchange for the release of five American detainees, was a sign of "appeasement" ahead of the surprise attack on Israel by Hamas militants.

"Not a single dollar from that account has been spent to date and, in any event, is very closely and carefully regulated by the Treasury Department," Blinken told ABC's "This Week" anchor George Stephanopoulos.

Blinken stressed that the funds are designated solely for humanitarian purposes and are not U.S. tax dollars.

-ABC News' Adam Carlson

In his first on-camera comments about Israel’s evacuation request for northern Gaza, Israeli Defense Minister Yoav Gallant urged Gaza residents to head south. He noted that Hamas will use them as "camouflage," “therefore we need to separate them."

"Those who want to save their life, please go south. We are going to destroy Hamas infrastructures, Hamas headquarters, Hamas military," he said.

Defense Secretary Lloyd Austin, who appeared at the press conference with Gallant, dodged ABC News' question about how Israel could end the Hamas terror threat without inevitably risking civilian lives. Austin called Israel's military "professional" and "disciplined."

Austin described how ISIS had also embedded themselves in civilian populations and how the anti-ISIS coalition "protected civilians and created corridors for humanitarian movement even in the midst of a pretty significant fight. So again, this is a professional force. It is well led, and I have every expectation that it will be disciplined."

Austin added, "I would tell you that in countering ISIS, I felt as if we were staring evil in the eye, it was truly evil. And what we've seen from Hamas, it takes that evil to another level."

-ABC News' Matt Seyler and Luis Martinez