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.

In remarks with Israeli Prime Minister Benjamin Netanyahu, Secretary of State Antony Blinken said at least 25 Americans had now been confirmed dead in Israel.

Netanyahu described some of the atrocities committed by Hamas.

"Hamas has shown itself to be an enemy of civilization: The massacring of young people in an outdoor music festival, the butchering of entire families, the murder of parents in front of their children and the murder of children in front of their parents. The burning of people alive, the beheadings," he said.

"Hamas should be treated exactly the way ISIS was treated," he said. "They shouldn't be spit out from the community of nations. No leader should meet them. No country should harbor them. And those that do should be sanctioned."

Blinken said he was speaking not only as an American diplomat, but as a Jew, a husband and a father of young children, saying it was impossible for him to look at photos of families killed "and not think of my own children."

"The same time that we've been shocked by the depravity of Hamas, we've also been inspired by the bravery of Israel citizens," he said. "The grandfather who drove over an hour to a kibbutz under siege, armed only with a pistol and rescued his kids and grandkids. The mother who died shielding her teenage son with her body, giving her life to save his -- giving him life for a second time."

Blinken remarked that some U.S. aid had already been delivered, and that more military aid was on his way. He said the administration would work with Congress to meet Israel’s additional needs and that bipartisan support for Israel was "overwhelming."

The secretary called on world leaders to condemn Hamas.

Blinken also reiterated that Israel "has the right -- indeed, the obligation -- to defend itself" but that it was "so important to take every possible precaution to avoid harming civilians."

-ABC News' Shannon Crawford