Alarmed US says document leak poses 'serious' security risk

The leak of highly sensitive US documents -- many of them related to the Ukraine conflict -- presents a "very serious" risk to US national security, the Pentagon said Monday.

The breach is being investigated by the Justice Department and appears to include secret information on the war in Ukraine as well as sensitive analyses of US allies, whom American officials are now seeking to reassure.

A steady drip of dozens of photographs of documents have been found on Twitter, Telegram, Discord and other sites in recent days, though some may have circulated online for weeks, if not months, before they began to receive media attention last week.

The documents circulating online pose "a very serious risk to national security and have the potential to spread disinformation," said Chris Meagher, assistant to the secretary of defense for public affairs, without confirming their authenticity.

"We're still investigating how this happened, as well as the scope of the issue. There have been steps to take a closer look at how this type of information is distributed and to whom," Meagher told journalists.

Many of the documents are no longer available on the sites where they first appeared, and the United States is reportedly continuing to work to have them removed.

Meagher said US Defense Secretary Lloyd Austin was not initially briefed on the issue until the morning of April 6 -- the day a New York Times story on the documents was published.

White House national security spokesman John Kirby told journalists that President Joe Biden was briefed on the leak "late last week," but did not provide a specific date.

Many of the documents relate to Ukraine, such as one that provides information on the country's air defenses or another on international efforts to build up its military forces.

- Reassuring allies -

But other documents point to US surveillance of its allies, such as one that states that leaders of Israel's Mossad intelligence agency advocated for domestic protests against a controversial judicial reform plan.

US officials have been in touch with Washington's allies over the issue, the State Department said.

They "are engaging with allies and partners at high levels over this, including to reassure them on our commitment to safeguarding intelligence and ability to secure our partnerships," spokesperson Vedant Patel told journalists.

The Pentagon also said relevant congressional committees have been informed.

Meagher said a Pentagon team is working to determine if the documents are genuine, but noted that images circulating online seemed to show sensitive information.

"Photos appear to show documents similar in format to those used to provide daily updates to our senior leaders on Ukraine and Russia-related operations, as well as other intelligence updates," he said, but some "appear to have been altered."

This includes a document that seems to have been altered to make it show that Ukraine had suffered higher casualties than Russia, when the apparent original version said the reverse was true.

Kirby said the US government is worried that there may be more documents to come.

"We don't know who's responsible for this. And we don't know if they have more that they intend to post," Kirby said, adding: "Is that a matter of concern to us? You're darn right it is."

The fallout from the apparent leak could be significant -- even deadly -- potentially putting US intelligence sources at risk while giving the country's foes valuable information.

"Disclosure of sensitive classified material can have tremendous implications not only for our national security, but could lead to people losing their lives," Meagher said.

'Significant' number of leaked US docs are fake

South Korea on Tuesday said a "significant portion" of leaked US intelligence documents indicating concerns in Seoul about arms supplies to Ukraine were fake.

The documents are part of a broader leak the Pentagon has described as a "very serious" national security risk. It has also created a diplomatic headache for Washington as they appear to show US spying on close allies including South Korea and Israel.

Some files reportedly show concern among top South Korean national security officials that arms and ammunition manufactured by their country might end up being used in Ukraine -- a violation of Seoul's policy of not selling weapons to nations at war.

In a call on Tuesday, the South Korean defence minister and the US secretary of defense agreed that "a significant number of the documents in question were fabricated", the presidential office in Seoul said in a statement.

Dozens of photographs of the documents have been circulating on social media platforms and messaging services including Twitter, Telegram and Discord for at least weeks.

The Pentagon has said it is working to determine if the documents are genuine, and that at least one appeared to have been manipulated.

However, US officials reportedly believe many of the documents are real.

The leak has prompted US officials to reassure allies such as South Korea, which has provided non-lethal and humanitarian aid to Ukraine since Russia invaded last year.

But Seoul has a long-standing policy against providing weapons to countries in active conflict, which it says makes it difficult to supply arms directly to Ukraine.

The revelation of the purported Ukraine discussions among top national security officials has sparked criticism in South Korea about the vulnerability of sensitive sites including the presidential office.

But President Yoon Suk Yeol's office pushed back Tuesday, saying it had "iron-clad security" and that allegations of eavesdropping were "senseless lies".

Yoon is scheduled to travel to the United States later this month on a state visit.

Who leaked top US documents - and why?

BBC in its report titled “Ukraine war: Who leaked top secret US documents – and why?” dug deep into how real are these printed pages, unfolded and photographed, possibly on someone's dining room table? And what do they tell us, or the Kremlin, that we did not already know?

They tell of the casualties suffered on both sides, the military vulnerabilities of each and, crucially, what their relative strengths are likely to be when Ukraine decides to launch its much-anticipated spring offensive.

Ukraine has zealously guarded its "operational security" and cannot be happy that such sensitive material has appeared at such a critical moment.

Ukraine's spring offensive could represent a make-or-break moment for the Zelensky government to alter dynamics on the battlefield and set conditions for peace talks later.

In Kyiv, officials have spoken about a possible disinformation campaign by Russia.

Other military bloggers have suggested the opposite: that it is all part of a Western plot to mislead Russian commanders.

Crucially, there is nothing in the documents leaked so far that points to the direction or thrust of Ukraine's counter-offensive.

The Kremlin ought to have a pretty good idea already of the scope of Ukraine's preparations (although Moscow's intelligence failures have been much in evidence throughout the war), but Kyiv needs to keep its enemy guessing about how the campaign will unfold, in order to maximise the chances of success.