Washington, May 16 The White House has denied that President Donald Trump revealed highly classified information about the Islamic State (IS) terror group to Russian Foreign Minister Sergey Lavrov, and claimed the reports as "false".

"The story that came out tonight (Monday night), as reported, is false ... At no time were intelligence sources or methods discussed," White House National Security Adviser H.R. McMaster said in a brief appearance before reporters.

"And the President did not disclose any military operations that were not already publicly known. Two other senior officials were present, including the Secretary of State, remembered the meeting the same way and said so. The on-the-record accounts should outweigh those of anonymous sources," McMaster said.

The Washington Post reported on Monday that Trump met with Lavrov and Russian Ambassador to Washington Sergey Kislyak in the Oval Office last week and revealed to them highly classified information concerning the possibility that the IS might use portable computers to carry out terrorist attacks on commercial flights, remarks to which McMaster did not allude in his denial.

McMaster also said that he had been present at the meeting.

Meanwhile, Secretary of State Rex Tillerson said: "During President Trump's meeting with Foreign Minister Lavrov, a broad range of subjects were discussed, among which were common efforts and threats regarding counter-terrorism."

"During that exchange, the nature of specific threats were discussed, but they did not discuss sources, methods or military operations," Tillerson added.

McMaster said the President and Lavrov "reviewed common threats from terrorist organisations to include threats to aviation," adding that "at no time were any intelligence sources or methods discussed and no military operations were disclosed that were not already known publicly."

The meeting with the Russian officials came a day after Trump fired Federal Bureau of Investigation (FBI) Director James Comey.

Comey had been heading an FBI probe into possible contacts between Trump's election campaign and the Kremlin.

US intelligence services have concluded that Russia interfered with the November presidential election to favour Trump.

White House denies Trump revealed classified info to Russians