Washington DC - The leak of a large trove of classified Pentagon documents is being taken "very seriously" and the potential risks to national security are being reviewed, the Biden administration said on Monday.

The documents, which surfaced this month on social media platforms like Twitter and Discord, contain US military secrets about Ukraine, China, and the Middle East, among other sensitive issues.

The Defense Department is leading a review to determine "whatever national security implications might come out of all this, and the Department of Justice is leading a criminal investigation," White House National Security Council spokesperson John Kirby said.

"So we're taking this very, very seriously. There is no excuse for these kinds of documents to be in the public domain."

The secret documents from US intelligence agencies have apparently been circulating on the internet for weeks – often in pro-Russian channels – and the intelligence details about the war in Ukraine have attracted particular attention.

The documents contain information on arms deliveries to Ukraine and concerns about Kiev's potential ammunition shortfalls. There is also information on alleged NATO and US plans on how the Ukrainian military is preparing for a spring offensive to retake territory from Russia.

There were also suggestions that the US has been spying on its allies, including Ukrainian President Volodymyr Zelensky, which Russia was quick to pounce on.

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Kirby said that in some instances, the documents posted online had been "altered from what we think would be the original source."

"But there's just no way I can tell you with any granularity right now how that came to be," he added.