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

Israeli leaders celebrated the killing of Hamas leader Yahya Sinwar, who was assassinated by Israeli forces on Thursday.

Israel President Isaac Herzog commended the Israel Defense Forces for the killing and said Israel must act in every way possible to bring back the remaining 101 hostages being held by Hamas in Gaza.

"Sinwar, the mastermind behind the deadly October 7th attack, has for years been responsible for heinous acts of terrorism against Israeli civilians, citizens of other countries, and the murder of thousands of innocent people. His evil endeavors were dedicated to terror, bloodshed, and destabilizing the Middle East," Herzog said in a statement.

Israeli Minister of Defense Yoav Gallant also saluted IDF soldiers.

"The elimination of Sinwar joins a long series of eliminations -- from Nasrallah to Muhammad Deif and many more. We will pursue and eliminate our enemies. Sinwar died while beaten, persecuted and on the run -- he didn’t die as a commander, but as someone who only cared for himself," Gallant said in a statement.

"This is a clear message to all of our enemies -- the IDF will reach anyone who attempts to harm the citizens of Israel or our security forces, and we will bring you to justice," Gallant said.

Benny Gantz, the former IDF chief of staff and former minister of defense, applauded the killing, but said "the mission is not over."

"The IDF will continue to operate in the Gaza Strip for years to come, and now the series of achievements and the elimination of Sinwar must be taken advantage of to bring about the return of the abductees and the replacement of Hamas' rule. On this day, we will also remember the painful price of the war, all the murdered and martyrs, and we will strengthen all our heroic soldiers who have been working for over a year in all arenas to ensure that never again," Gantz said.

-ABC News' Jordana Miller