Documents purporting to show classified U.S. intelligence-gathering on Israel's preparations for a possible retaliatory strike against Iran appeared on social media platforms late last week.

The impact of the circulation of these documents on current and future planning by the Israeli military is unclear at this time.

U.S. officials declined to comment on the situation when reached by ABC News. However, a law enforcement source on Sunday confirmed with ABC News that there is an investigation underway.

Markings on the documents indicate that they would have originated from the National Geospatial-Intelligence Agency, which collects, analyzes and distributes intelligence gleaned from satellite and aerial imagery.

If the documents are authentic, it would indicate a major intelligence breach.

According to Mick Mulroy, an ABC News national security and defense contributor, who served as the deputy assistant secretary of defense for the Middle East: "The future coordination between the U.S. and Israel could be challenged, as well."

The Department of Defense, Federal Bureau of Investigation and a spokesperson for the Office of the Director of National Intelligence all declined to comment when contacted by ABC News.

House Speaker Mike Johnson appeared on CNN Sunday and acknowledged that there is an investigation underway into the possible intelligence leak, adding, "We're following it closely."

-ABC News' T. Michelle Murphy

The Israel Defense Forces announced it was targeting infrastructure Sunday night in Lebanon that has been linked to the Al-Qard Al-Hassan Association, an organization it alleges is involved in financing Hezbollah.

The United States placed sanctions on the Al-Qard Al-Hassan Association in May 2021 related to financing Hezbollah activities.

The Al-Qard Al-Hassan group has 31 branches in Lebanon -- including in Beirut and Bekaa, officials said. At least one strike was reported Sunday evening in the Chyah neighborhood of Beirut.

"The 'Al-Qard Al-Hassan Association' is involved in financing the terrorist activities of the Hezbollah organization against Israel, and therefore the IDF has decided to attack this terrorist infrastructure," the IDF said in a statement Sunday. "The IDF continues to work forcefully to destroy Hezbollah's terrorist infrastructure. Therefore, we call on people inside buildings used by Hezbollah to stay at least 500 meters away from them for the next few hours."

-ABC News' Victoria Beaule

The IDF has announced the death of a colonel, 41-year-old Ehsan Daxa, in fighting in northern Gaza on Sunday.

Daxa is one of the highest-ranking IDF officers to be killed in the war. He commanded the 401st "Iron Tracks" Brigade of the 162nd Division, the IDF said.

-ABC News' Jordana Miller

At least 160 rockets fired by Hezbollah crossed from Lebanon into Israel on Sunday, Israel Defense Forces said, as sirens sounded across northwest Israel, including Haifa, the country's third largest city.

The IDF said the barrage of rockets occurred around 3 p.m. local time and that 30 projectiles crossed into Israel three minutes after they were launched.

No injuries or casualties have been reported. The IDF said some projectiles fell in the north and fire services were working to extinguish the fires that erupted from the attack.

-ABC News' Jordana Miller

National security communications adviser John Kirby called Hamas leader Yahya Sinwar’s death an "inflection point" in this war, providing a new opportunity to reach a cease-fire deal.

"So Hamas is in a much, much, much weakened position than it ever was before," Kirby told reporters in Berlin, where he is visiting alongside Joe Biden. "The president believes that certainly with Sinwar's killing yesterday, that there's a unique opportunity here for us all to kind of grab hold of to see what we can do to end the war and to get a cease-fire. And we still believe that a cease-fire, actually in the north too, but we still believe a cease-fire is important for Gaza to get those hostages home."

When pressed by reporters on what makes the White House so confident that Sinwar's death truly does open the door to achieve a deal that had not been possible for months, Kirby said that it's a "unique opportunity" to take the intensive diplomacy to the next level. Kirby also explained why it was difficult to negotiate with Sinwar.

"Every time his political advisers would -- we would negotiate with and through them to come up with a proposal, it would have to get to him," Kirby said. "Of course, that took time because of the communications challenges, and then he would just, he would just refute it and refuse to move forward."

-ABC News' Michelle Stoddart