Israel’s plans to attack Iran.

One of the documents, which says it was compiled by the National Geospatial-Intelligence Agency, says the plans involve Israel moving munitions around.

The leak is “deeply concerning,” a US official told CNN.

The documents, dated October 15 and 16, began circulating online Friday after being posted on Telegram by an account called “Middle East Spectator.”

The US is investigating a leak of highly classified US intelligence about Israel’s plans for retaliation against Iran, according to three people familiar with the matter. One of the people familiar confirmed the documents’ authenticity.

They are marked top secret and have markings indicating they are meant to be seen only by the US and its “Five Eyes” allies — Australia, Canada, New Zealand and the United Kingdom.

Another document says it is sourced to the National Security Agency and outlines Israeli air force exercises involving air-to-surface missiles, also believed to be in preparation for a strike on Iran. CNN is not quoting directly from or showing the documents.

A US official said the investigation is examining who had access to the alleged Pentagon document. Any such leak would automatically trigger an investigation by the FBI alongside the Pentagon and US intelligence agencies. The FBI declined to comment.

The leak comes at an extremely sensitive moment in US-Israeli relations and is bound to anger the Israelis, who have been preparing to strike Iran in response to Iran’s missile barrage on October 1.

“If it is true that Israeli tactical plans to respond to Iran’s attack on October 1 have been leaked, it is a serious breach,” said Mick Mulroy, former deputy assistant secretary of defense for the Middle East and a retired CIA officer.

They describe preparations Israel appears to be making for a strike against Iran.