Two Israeli tourists and their Egyptian guide were killed Sunday when a gunman opened fire on them and a group of travelers in Egypt, according to the Israeli Foreign Ministry.

The attack unfolded in Alexandria and was allegedly committed by a local resident, the Foreign Ministry said. The tour guide was an Egyptian, according to the Foreign Ministry.

The shooting left at least one other Israeli tourist injured, the Foreign Ministry said.

Israeli officials -- including the Israeli Embassy in Cairo, the Prime Minister's Office and the Israel Defense Forces -- are working with Egyptian authorities to return the slain Israeli citizens to Israel as soon as possible, the Foreign Ministry said.

-ABC News' Becky Perlow

More than 500 people have been killed in Israel and another 2,000 injured as rocket attacks and fighting continued between Israeli forces and Hamas militants, the Israeli Health Ministry said Sunday.

At least 30 Israeli police officers have been killed in the fighting, mainly in Sderot, where Hamas gunmen took control of the police station.

Meanwhile, fighting is still ongoing in six places, including Sderot -- which sits just two miles from the border with Gaza -- even after the police headquarters standoff ended and a rocket injured four people on Sunday morning.

On Saturday, graphic video showed dozens of dead bodies, bullet ridden homes and vehicles following an assault by armed militants.

Israel has also opened a hotline for family members who can come forward to give DNA samples to help identify those who have died.

Early Sunday morning, Israel police said in a statement, "The first phase ends in these hours by the destruction of the majority of the enemy forces that penetrated our territory. At the same time we started the offensive formation and it will continue without reservation and without respite until the objectives are achieved."

Israeli police announced the cabinet decided the supply of electricity, fuel and goods to the Gaza Strip will be suspended.

"We will restore security to the citizens of Israel and we will win," Israeli police said.

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."