U.S. President Donald Trump disclosed highly classified information to the Russian foreign minister about a planned ISIS operation during their meeting last week, two U.S. officials with knowledge of the situation said on Monday.

The intelligence shared at the meeting with Russian Foreign Minister Sergei Lavrov and Russian Ambassador Sergei Kislyak was supplied by a U.S. ally in the fight against the militant group, both officials said.

In his conversations with the Russian officials, Trump appeared to be boasting about his knowledge of the looming threats, telling them he was briefed on "great intel every day," an official with knowledge of the exchange said, according to the Post.

The White House said the allegations, first reported by the Washington Post, were not correct.

"The story that came out tonight as reported is false," H.R. McMaster, Trump's national security adviser, told reporters at the White House, adding that the two men reviewed a range of common threats including to civil aviation.

'I was in the room. It didn't happen' - National Security Adviser H.R. McMaster

"At no time were intelligence sources or methods discussed. The president did not disclose any military operations that were not already publicly known … I was in the room. It didn't happen," he said.

The White House also released a statement from Secretary of State Rex Tillerson, who said the meeting focused on counterterrorism, and from deputy national security adviser Dina Powell, who said the Post story was false.

On Tuesday morning, Interfax news agency cited the Russian Foreign Ministry as saying the reports are "fake."

Trump said on Twitter on Tuesday that he has the "absolute right" to share with Russia "facts pertaining to terrorism and airline safety." He said he wants Moscow to "greatly step up their fight against ISIS and terrorism."

'Very, very troubling'

Reacting to the news, the Senate's No. 2 Democrat, Dick Durbin, called Trump's conduct "dangerous" and "reckless." The Republican head of the Senate foreign relations committee, Bob Corker, called the allegations "very, very troubling" if true.

The latest controversy in the White House came as it continued to reel from the fallout over Trump's abrupt firing of FBI Director James Comey last week and amid congressional calls for an independent investigation into allegations of Russian meddling in the 2016 U.S. election.

On Monday, one of the officials said the intelligence was classified "Top Secret" and also held in a secure "compartment" to which only a handful of intelligence officials have access.

After Trump disclosed the information, which one of the officials described as spontaneous, officials immediately called the CIA and the National Security Agency, both of which have agreements with a number of allied intelligence services, and informed them what had happened.

While the president has the authority to disclose even the most highly classified information at will, in this case he did so without consulting the ally that provided it, which threatens to jeopardize what they called a long-standing intelligence-sharing agreement, the U.S. officials said.

Officials refuse to answer questions on specifics

Closed-door emergency meetings. Hallways packed with reporters. Statements rushed out, but few questions answered.

It's become a familiar scenario in the crisis-prone Trump White House, where big news breaks fast and the aides paid to respond seem perpetually caught off-guard.

The Post report sent Trump's communications team into a tizzy.

There was a surprise encounter between reporters and McMaster, and an attempt to drown out conversations with a blaring television.

White House officials denied the story in several statements, including a 45-second on-camera statement delivered by McMaster. But officials refused to answer specific questions, including what precisely the report had gotten wrong, ensuring it would dominate a week that White House officials hoped would be quiet in advance of the president's first foreign trip.

Reporters started gathering in the hallway outside Press Secretary Sean Spicer's office right after the Post story broke. As the group grew to more than 20 people, press aides walked silently by as journalists asked for more information. Soon, three of the four TV channels being played in the press area were reporting the Post story.

At one point, McMaster, who would later deliver the televised denial, stumbled into the crowd of journalists as he walked through the West Wing.

"This is the last place in the world I wanted to be," he said, nervously, as he was pushed for information. "I'm leaving. I'm leaving."

Not long after, the press office sent a trio of short, written statements. Then Spicer briefly appeared to say McMaster would speak outside soon, prompting a mass exodus to a bank of microphones set up in the West Wing driveway before McMaster made his brief statement that the Post story was incorrect.

But what, precisely, had been misreported?

The Post story said the information Trump shared, which had been provided by a U.S. partner through an intelligence-sharing arrangement, was considered so sensitive that details have been withheld from allies and tightly restricted even within the U.S. government.

The Post story did not claim that Trump revealed any specific information about how the intelligence was gathered, as McMaster's denial suggested.

Reporters immediately returned to Spicer's office, hungry for answers.

As they huddled in a hallway, one reporter for the conservative One America News Network spotted a handful of staffers, including Spicer and spokeswoman Sarah Huckabee Sanders, walking not far from Spicer's office.

Soon after, faint, muffled sounds were heard coming from that direction.

It was unclear precisely where they were coming from or what they were — but after a reporter tweeted about the noise, White House staffers quickly turned up the volume on the office television, blaring a newscast loudly enough to drown out any other potential noise.

Around 7:30 p.m., Sanders emerged to announce that White House officials would not be answering any more questions for the evening.

"We've said all we're going to say," she said.

Trump 'has no filter,' says official

U.S. officials have told Reuters they have long been concerned about disclosing highly classified intelligence to Trump.

One official, who requested anonymity to discuss dealing with the president, said last month: "He has no filter; it's in one ear and out the mouth."

USA TRUMP LAVROV

Trump is shown with Lavrov during last week's meeting. At the time, U.S. Secretary of State Rex Tillerson said in a statement that two discussed a broad range of subjects. (Russian Foreign Ministry/EPA)

One of the officials with knowledge of Trump's meeting with the Russians called the timing of the disclosure "particularly unfortunate," as the president prepares for a White House meeting on Tuesday with Turkish President Tayyip Erdogan, an ally in the fight against ISIS.

Trump's first foreign trip also begins later this week and includes a stop in Saudi Arabia, another ISIS foe, and a May 25 NATO meeting in Brussels attended by other important U.S. allies.

Trump, a Republican who has called allegations of links between his presidential campaign and Russia a "total scam," has sharply criticized his 2016 election rival, Democrat Hillary Clinton, for her handling of classified information as secretary of state, when she used a private email server.

The FBI concluded that no criminal charges were warranted, but Comey said she and her colleagues had been "careless" with classified information.

With files from CBC News and The Associated Press