Up to 50 Israelis who were being held hostage by Hamas have been freed, according to an Israel Defense Forces spokesperson.

They were being held in the dining hall of Kibbutz Be'eri in southern Israel, though the situation has been "neutralized," the IDF spokesperson said.

Officials still believe hostages are being held in Gaza but an exact number hasn't been released.

The FBI and the Department of Homeland Security have issued a "Public Safety Notification" to law enforcement around the U.S., urging them to remain vigilant and report any suspicious activity in the midst of the ongoing situation in Israel.

The notice says the agencies "do not currently have specific intelligence indicating a threat to the United States stemming from the Hamas attacks in Israel" but that "foreign terrorist organizations and their supporters remain committed to attacking the United States within and beyond our borders."

"In recent years, there have been several events and incidents in the United States that were purportedly motivated, at least in part, by the conflict between Israel and Hamas," the notice continued. "These have included the targeting of individuals, houses of worship, and institutions associated with the Jewish and Muslim faiths with acts of physical assault, vandalism, or harassment."

-ABC News' Mike Levine

A high-ranking Israel Defense Forces commander was killed in action Saturday, the military said.

Col. Jonathan Steinberg, 42, the commander of the Nahal Brigade, was killed during a confrontation with Hamas, IDF said.

United Hatzalah, a community-based volunteer EMS organization, said so far it has treated nearly 1,000 people for "various injuries" in southern and central Israel.

The organization said it has also transported an unspecified number of patients to hospitals in the regions via ambulance and helicopter.

The United States is warning against other countries from becoming involved in the Israel-Gaza conflict amid fears that it could spread into a wider war in the Middle East.

"This is not the moment for other parties who are hostile to Israel to seek advantage or to seek to exploit the attacks that have taken place," Jon Finer, deputy national security adviser to U.S. President Joe Biden, Monday on "Good Morning America."

"That is part of why the United States has moved the Carrier Strike Group to the eastern Mediterranean to send a strong and unmistakeable signal that no one else should get involved in this," he added. "We'll see how things unfold in the course of the coming days."

Finer also emphasized that the U.S. believes "Israel has every right to defend itself full-stop."

"Israel will ultimately make the decisions about how it chooses to go about and conduct that defense," he said. "We are offering support in a number of ways."

Finer noted that "more U.S. steps to show support and solidarity for Israel" can be expected.

"The U.S. is going to offer support at every level for Israel's defense and we are working through details those details with our intelligence professionals, our military and our diplomats," he added. "We are in daily -- in fact, many times a day -- contact with Israeli counterparts to see what they need and offer it."

The U.S. "strongly suspect[s] that there will be American citizens among those killed" in the ongoing conflict, according to Finer.

"We are looking obviously very intensively into whether there were any Americans were among those who have been abducted and brought to Gaza. This is still ongoing," he said. "There is still fighting inside Israel as we speak and there is a bit of fog of war in terms of the ability to gather specific information. And so, we will have much more to say about this at the right time."

When asked for comment on a recent report by The Wall Street Journal that Iran was behind Hamas' latest attack on Israel, Finer responded: "We have no direct information to confirm that report. We've obviously seen it, we're looking into it, but we do not have the ability to corroborate it at this time."

"What we can be quite clear about is that Iran is broadly complicit in these attacks for having supported Hamas going back decades -- for having provided financial support, for having provided training, for having provided weapons to Hamas," he added. "What we don't have is direct information that shows Iranian involvement in ordering or planning the attacks that took place over the last couple days. It's something that we’re going to keep looking at closely."