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.

National Security Council spokesperson John Kirby avoided saying if the U.S. believed Israel's calls for civilians in Gaza to evacuate in the next 24 hours was possible but acknowledge that it was a "tall order" given how densely populated the area is.

"Well, I think we're going to be careful not to get into armchair quarterbacking the tactics on the ground by the IDF. What I can tell you is we understand what they're trying to do. They're trying to move civilians out of harm's way and giving them fair warning. Now, it's a tall order. It's a million people, and it's a very urban, dense environment, already a combat zone. I don't think anybody's underestimating the challenge here of affecting that evacuation," Kirby said in an interview on CNN Friday morning.

"But it's pretty clear that what they're trying to do is to the maximum extent possible avoid civilian casualties and also separate Hamas from the human shields. I mean, Hamas actually gave a counterorder telling Palestinians in Gaza to stay at home. Why? Because having human shields, they think, protects them," Kirby continued.

Asked about their efforts to secure a safe passage for civilians out of Gaza, Kirby reiterated that the U.S. is talking to Israel and Egypt but would not comment further on progress.

On the Rafah crossing specifically, Kirby said "So far it's still closed. But that doesn't mean were not going to still try as hard as we can to talk to the Israelis and Egyptians about getting it open and having some sort of safe passage out. It's important that we also continue to work to make sure that humanitarian assistance can get in. The United States has no intention of stopping our efforts to continue to deliver humanitarian assistance, but there has to be a path in, there has to be a path out."

Kirby had no update on the Americans who are believed to be held hostage in Gaza and could not confirm reports that 13 hostages have been killed by Israeli airstrikes, as Hamas has claimed.

-ABC News' Molly Nagle