Personnel at the U.S. Embassy in Israel are now under a curfew from 8 p.m. to 6 a.m. and "are urged to stay as close to home as possible outside the curfew hours," the U.S. Embassy said in a new alert.

In addition to a ban on personal travel to Gaza and the surrounding areas, the new alert said all U.S. government personnel are also prohibited from personal travel to the West Bank.

"U.S. citizens in Israel who have family members missing in the Gaza periphery can go to the Israel National Police’s combined assistance center at 4 HaNegev Street in Airport City," the alert said.

-ABC News' Shannon Crawford

Israel Defense Forces' helicopter gunships are attacking Lebanese territory on Monday after the IDF said two rockets were fired from Lebanon.

The Lebanese army said, "The outskirts of the towns of Al-Dhaira and Aita Al-Shaab and other border areas are being subjected to air and artillery bombardment by the Israeli enemy. The Army Command calls on citizens to take the utmost precaution and caution and not to go to areas adjacent to the border in order to preserve their safety."

Of the two rockets fired from Lebanon toward Israel, one of the rockets fell in Lebanese territory and no injuries were reported.

At least nine Americans have been killed in Israel since Saturday as a result of attacks launched by the Hamas militant group, according to an official with the United States National Security Council.

"At this time, we can confirm the death of nine U.S. citizens," the official told ABC News in a statement on Monday. "We extend our deepest condolences to the victims and to the families of all those affected, and wish those injured a speedy recovery. We continue to monitor the situation closely and remain in touch with our Israeli partners, particularly the local authorities."

Two French citizens are among those killed in Israel, the French Foreign Ministry said.

-ABC News' Molly Nagle

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.

"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."

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US pledges support to Israel after deadly surprise attack

Deputy national security adviser Jon Finer discusses how the Biden administration is prepared to support Israel in the midst of the deadly conflict with Hamas.