David Friedman, former U.S. ambassador to Israel during the Trump administration, said he has never seen borders breached like this, calling it an "intelligence failure."

"In the 40 or more years that I’ve been following Israel one way or another, I’ve never seen this happen," he said in an interview today. "I’ve never seen the border breached in this manner. Usually, even if one person from Gaza gets close to the border, they’re intercepted and neutralized long before they can do anything."

Friedman said he thinks President Joe Biden’s administration should encourage and "support Israel to do what Israel thinks is necessary to restore deterrence and restore stability to its own country."

The attack has left many people angry over what happened and "feeling very fragile."

"What’s really troubling about this is that there are so many civilian casualties and the pictures of Israelis being shoved into Jeeps and taken into Gaza," Friedman said. "This has never happened before. There’s such a sense of vulnerability."

Obama-era deputy national security adviser Ben Rhodes said on MSNBC that the scale of today's attack suggests it would have taken months for Hamas to plan and acquire more advanced weaponry. He said that, in the past, the militant group has relied primarily on rockets fired in Israel or more discreet attacks.

"I think what is surprising is the scale and complexity of this attack," said Rhodes on MSNBC. "We’ve not seen Hamas undertake something of this ambition, where they’re acting with so many different tactics and in so many different ways."

Rhodes said that although the buildup of violence between Israelis and Palestinians had already created a "tinder box," the current situation will launch Israel and Palestine into a new political reality.

"It's going to completely remake the circumstance politically in terms of the Palestinian leadership - it's obviously entering into a volatile moment in Israeli politics," said Rhodes. This can get much more complicated so we are definitely in a new reality today."

President Joe Biden will offer remarks on "the terrorist attacks in Israel" at 2:30 p.m. ET, the White House said.

Al-Qassam Brigades, the armed wing of Hamas, said it fired another strike with 150 missiles toward Tel Aviv.

The strike was in response to the bombing of a residential tower in the center of Gaza City around 8 p.m. (1 p.m. ET), Al-Qassam Brigades said.

Flights operated by American, United and Delta Airlines out of major U.S. cities like Chicago, New York and San Francisco bound for Tel Aviv have been canceled amid the ongoing conflict, FlightAware data shows.

About 15% of flights destined to Ben Gurion International Airport in Tel Aviv have been canceled and 21% were delayed Saturday, according to FlightAware.

Delta and American Airlines said they have canceled scheduled flights into and out of Tel Aviv through the weekend. 

A Delta spokesperson said the airline is working to “safely transport Delta people back to the U.S. and will work with the U.S. government as needed to assist with the repatriation of U.S. citizens who want to return home.”

Last night, Tel Aviv-bound United Airlines Flight 954 departed from San Francisco International Airport and diverted over Greenland to head back to its origin airport after about seven hours in the air, FlightAware data shows. 

United said it’s “closely minoring the situation” and “adjusting flight schedules as required.” Aside from two departures from Tel Aviv scheduled for Saturday, future operations will be suspended, the airline said.

Israel's arch-enemy Iran celebrated Hamas's attack on Saturday, saying it demonstrated that "Palestinian resistance" was able to carry out "hybrid and multilateral operations."

The operation proved that Israel was vulnerable in the face to serious attack, Foreign Ministry spokesperson Nasser Kanaani said.

Iran does not recognize Israel's right to exist, often referring to it as the "Zionist entity," and has supported Hamas, along with other militant groups in the region.

The International Rescue Committee mourned the loss of life in Israel and Gaza today and said it's assessing civilian needs on the ground, according to a statement.

“We are dismayed by the dramatic escalation of violence and mourn the extensive loss of civilian life in Israel and Gaza today," the statement read. "We are focused on the humanitarian needs of civilians in the coming days. We are assessing needs on the ground and IRC’s capacity to ensure critical, life-saving humanitarian relief reaches affected civilian populations."

The organization also called on the parties involved "to uphold their obligations under International Humanitarian Law and ensure humanitarian access to those affected.”

Ukranian President Volodymyr Zelenskyy, who remains at war with Russia, offered assistance to Israel and denounced Hamas' actions.

"Terror should have no place in the world, because it is always a crime, not just against a specific country or this terror’s victims, but against humanity in general and our entire world," Zelenskyy wrote in a Facebook post Saturday.

The Ukrainian Ministry of Foreign Affairs and the embassy in Israel have created an operational headquarters to assist Ukrainian citizens. Zelenskyy asked Ukrainians abroad to reach out to access consular services.

"All Ukrainian citizens who remain in the risk zone must carefully obey all orders issued by local security services and remain vigilant," he wrote. "Please be cautious."