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Days after President Donald Trump met with top-level Russian diplomats last week—an Oval Office meeting that was closed to American media—the Washington Post reports the president shared “highly classified” information with both the Russian ambassador and foreign minister—allegations based on accounts provided to the Post by anonymous “current and former U.S. officials.”

According to the Post, this sensitive information concerned “elements of a specific plot” by the Islamic State:

The information Trump relayed had been provided by a U.S. partner through an intelligence-sharing arrangement considered so sensitive that details have been withheld from allies and tightly restricted even within the U.S. government, officials said. The partner had not given the United States permission to share the material with Russia, and officials said that Trump’s decision to do so risks cooperation from an ally that has access to the inner workings of the Islamic State. After Trump’s meeting, senior White House officials took steps to contain the damage, placing calls to the CIA and National Security Agency. “This is code-word information,” said a U.S. official familiar with the matter, using terminology that refers to one of the highest classification levels used by American spy agencies. Trump “revealed more information to the Russian ambassador than we have shared with our own allies.”

As the Post notes, the president has broad authority to declassify pieces of information at his choosing, but “for most anyone in government, discussing such matters with an adversary would be illegal.” (The National Security Agency and the CIA declined to provide comment to the Post.)

Two US officials confirmed the Post’s account to BuzzFeed News late Monday afternoon, with one official adding that “it’s far worse than what has already been reported.”

Trump reportedly revealed highly classified information to Russians during White House visithttps://t.co/KkqjhFwXFe pic.twitter.com/qfv6HYz9FR — BuzzFeed News (@BuzzFeedNews) May 15, 2017

Head to the Washington Post for the full account.