US President Donald Trump disclosed highly classified information to Russia's foreign minister about a planned Islamic State 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.

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.

"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 focussed on counterterrorism, and from deputy national security adviser Dina Powell, who said the Washington Post story was false.

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 discussed by Trump in the meeting with Lavrov was classified "Top Secret" and 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 jeopardise what they called a long-standing intelligence-sharing agreement, the U.S. officials said.

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.


'NO FILTER'

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.

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.”

One of the officials with knowledge of Trump's meeting with the Russian 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 Islamic State.

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