The US has launched an investigation into the leaking of two alleged intelligence documents that detailed Israel’s preparation for a potential strike on Iran in the coming days.

The documents, seen by The Telegraph, include interpretations of satellite imagery that appear to have been prepared recently by the National Geospatial-Intelligence Agency (NGA), and analyse information gathered by US spy satellites and the National Security Agency.

They were marked “top secret”, dated Oct 15 and 16 and were circulated on Friday night on the Telegram messaging app.

One document says Israel continues to prepare munitions and covert drone activity, while the other outlines Israeli Air Force exercises involving ballistic and air-to-surface missiles.

Both say the activities were believed to be in preparation for a strike on Iran. The Telegram channel accused at first of leaking the documents said the documents initially appeared in a separate private group with 7,000 members.

Notes are ‘US assessment of events’

“We also reiterate that we have no connection to the original source, which we assume to be a whistleblower within the US Department of Defence,” the statement said. In a separate statement, the Telegram group said an acquaintance had received the documents through an anonymous source.

The group claims to be run by independent journalists and that it is not “Iran-affiliated”, but it refers to the Israeli government as the “Zionist regime” and uses Tehran time as a baseline.

The New York Times reported that the documents have been discussed by largely pro-Iran accounts on Telegram since Friday.

The documents do not appear to be a comprehensive assessment of Israeli intentions but an assessment of developments by the US on the dates given.

An Israeli reprisal against Iran has been expected since Iran launched its own retaliatory assault on Oct 1, launching 200 ballistic missiles at Israeli targets in at least two waves.

The Iranian attack was a response to the killings of senior Hamas and Hezbollah leaders.

US officials told CNN that the leak is “deeply concerning”, while privately acknowledging they are authentic to The New York Times.

The US is said to be investigating who had access to the alleged classified documents.

Two years ago, a large leak of classified material appeared on Discord and was made public last year. It was one of the biggest leaks of government secrets in US history.

On Friday, Joe Biden, the US president, said during a visit to Germany that he has a good understanding of how and when Israel plans to respond to Iran’s recent ballistic missile attack.

The remarks were the first time the US has indicated that an understanding has been reached with Israel on the nature of the retaliation. Mr Biden has previously said he opposed Israel targeting Iranian nuclear or oil sites.