THE United States is investigating an unauthorised release of classified documents that assess Israel’s plan to attack Iran, according to three US officials.

The documents, attributed to the US Geospatial Intelligence Agency and National Security Agency and marked “top secret,” indicate that Israel is moving military assets into place to carry out a military strike in response to Iran’s ballistic missile attack on October 1.

US House speaker Mike Johnson confirmed the investigation in remarks to CNN’s State of the Union programme on Sunday, saying the “leak is very concerning”.

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The investigation is also examining how the documents were obtained, including whether or not it was an intentional leak by someone within the US intelligence community or if they were obtained via another method.

The documents first appeared online on Friday via a channel on Telegram, claiming they had been leaked by someone in the US intelligence community, then later the US Defence Department.

The information appeared to have been gathered through the use of satellite image analysis.

The channel involved in the leak identified itself as being based in Tehran – Iran’s capital.

Israeli strikes on multiple homes in the northern Gaza Strip overnight and into Sunday have left at least 87 people dead or missing, the territory’s Health Ministry said.

It said another 40 people were injured in the strikes on the town of Beit Lahiya, which was among the first targets of Israel’s ground invasion nearly a year ago.

There was no immediate comment on the strikes in Beit Lahiya from the Israeli military, which said it is “continuing to operate across Gaza in both aerial strikes and ground operations”.

Among the dead were two adults and their four children, and a woman, her son and daughter-in-law and their four children, according to Raheem Kheder, a medic. He said the strike flattened a multi-storey building and at least four neighbouring houses.

Mounir al-Bursh, director-general of the Health Ministry, said in a post on social media site X that the flood of wounded from the strikes has compounded “an already catastrophic situation for the healthcare system” in northern Gaza.

Internet connectivity went down in northern Gaza late on Saturday and had not been restored by midday on Sunday, making it difficult to gather information about the strikes.

Israel has been carrying out a major operation in the urban Jabaliya refugee camp, also in northern Gaza, for the last two weeks. The military said it launched the operation against Hamas militants who had regrouped there.

The north has already suffered the heaviest destruction of the war, and has been encircled by Israeli forces since late last year, following Hamas’s deadly attack on Israel on October 7.

Israel ordered the entire population of the northern third of Gaza, including Gaza City, to evacuate to the south in the opening weeks of the war and reiterated those instructions earlier this month.

Most of the population fled last year, but around 400,000 people are believed to have remained in the north.