For an operation now dubbed "Swords of Iron," the Israel Defense Forces said Monday that it had struck 500 Hamas and Islamic Jihad targets in the Gaza Strip.

The attacks were carried out through the use of jets, helicopters and other aircraft, according to the IDF.

The IDF said seven of Hamas' command centers were struck in the mission.

-ABC News' Bruno Nota

An Iranian official at the UN denied that Iran had any involvement in Hamas' attack on Israel.

Israeli officials, including President Isaac Herzog, had claimed on Saturday that Iran helped coordinate the attacks on Israel.

On Sunday, however, Iran's Mission to the UN, denied the claims.

“We emphatically stand in unflinching support of Palestine; however, we are not involved in Palestine's response, as it is taken solely by Palestine itself.,” the Iranian Mission to the UN said in a statement late Sunday. “The resolute measures taken by Palestine constitute a wholly legitimate defense against seven decades of oppressive occupation and heinous crimes committed by the illegitimate Zionist regime.”

A U.S. official said Saturday it was "too early" to tell if Iran had involvement in the attacks.

"We are going to be looking at that very closely," a senior administration official said.

-ABC News' Kirit Radia

Israeli Defense Forces attacked the Gaza Strip early Monday morning local time, the IDF said in a series of posts on X, the platform formerly known as Twitter.

The IDF attacked a building where it said Hamas operatives were and several operational headquarters of the organization, the IDF said in the posts.

-ABC News’ Ellie Kaufman

An emergency meeting of the United Nations Security Council failed to condemn the Hamas attacks on Israel Sunday evening.

Deputy U.S. Ambassador the U.N. Robert Wood said the situation was "still fluid" and "very dangerous."

"What is important now is that the international community needs to show its solidarity with Israel. We have Israel's back fully as the United States, and the condemnation of Hamas needs to continue until they end this violent terrorist activity against the Israeli people," Wood said after the meeting.

-ABC News' Ellie Kaufman

Human Rights Watch has accused Israel of using white phosphorus munitions in military operations in Gaza on Wednesday, saying it violated international humanitarian law by putting civilians at unnecessary risk.

In a report released Thursday, Human Rights Watch said it based its determination on a video it said it has verified, as well as two eyewitness accounts.

The Israel Defense Forces said in a statement to ABC News that claims they used white phosphorus in Gaza are "unequivocally false."

ABC News geolocated a video showing a jellyfish-shaped plume of white smoke over the port of Gaza. The video was posted on Wednesday by the official Palestinian news agency WAFA and matches images posted on social media and by other news outlets on the day.

Two experts -- Amael Kotlarski, the weapons team manager for the defense intelligence firm Janes, and Amnesty International weapons investigator Brian Castner -- told ABC News that images suggested munitions deployed over the port of Gaza on Wednesday appeared to contain white phosphorus.

"We have verified that Israeli artillery forces striking Gaza are equipped with M825 and M825A1155mm white phosphorus projectiles," Castner told ABC News, pointing to photographs by an Anadolu Agency photographer taken on Monday and showing Israeli troops handling shells labeled "M825A1."

Kotlarski said visual evidence alone was not sufficient to confirm that these specific shells were used in the Gaza port strikes.

There are "perfectly legal" military uses for white phosphorus munitions, Kotlarski said, including to create a smoke screen to conceal movements, to mark targets for artillery or air strikes, or to illuminate a battlefield. However, its use in urban areas is "problematic due to the higher risk of collateral damage," Kotlarski said, including the munitions' potential to cause severe burns.

White House Principal Deputy Press Secretary Olivia Dalton said Friday the U.S. had not independently verified allegations Israel used white phosphorous "so that is not something I would want to speculate about or weigh in on at this time."

-ABC News' Christopher Looft, Ben Gittleson and Jordana Miller