WASHINGTON — The White House, already embroiled in a self-inflicted crisis, lurched into a new one Monday as administration officials and members of Congress reacted to reports that President Donald Trump had shared highly classified intelligence with visiting Russian officials in the Oval Office.

Not even a week removed from the president’s stunning decision to fire FBI Director James B. Comey, which was followed by days of often conflicting White House explanations, administration officials sought to deny the story that was first reported by The Washington Post. The discussion between Trump and the Russians covered only a range of common threats and did not include operations not already publicly disclosed, White House officials said.

In a brief and hastily scheduled appearance before reporters outside the West Wing, national security adviser H.R. McMaster said that “at no time were intelligence sources or methods discussed” in the meeting. “I was in the room. It did not happen,” McMaster said before leaving without answering shouted questions.

That was, however, a denial of a claim that the Post article had not made. The article said Trump discussed information at one of the highest classification levels, about threats from the Islamic State involving laptops taken aboard airliners, during his meeting with Russian Foreign Minister Sergei Lavrov and Ambassador Sergey Kislyak.

The information had come from a U.S. ally that had provided the intelligence on condition it not be shared, the Post said. That breach of the intelligence-sharing relationship could make Trump’s disclosure especially damaging, the newspaper reported.

The Post stood by its reporting, and The New York Times reported a similar account soon after the Post.

Even as the White House disputed the reports, some Republican senators seemed to credit them, expressing dismay instead of coming to Trump’s defense.

“The White House has got to do something soon to bring itself under control and in order,” said Sen. Bob Corker of Tennessee, the Republican chairman of the Senate Foreign Relations Committee. “Obviously they’re in a downward spiral right now, and they’ve got to figure out a way to come to grips with all that’s happening.”

Democrats in Maryland’s congressional delegation reacted quickly to the report, calling it “distressing” and “dangerous.” The lawmakers acknowledged they had not independently verified the allegations but were instead responding to news coverage.

“After an unprecedented week in which many thought it would be impossible for President Trump to be any more irresponsible, he now may have sunk to a dangerous new low,” said Rep. Elijah E. Cummings of Baltimore, the top-ranking Democrat on the House Committee on Oversight and Government Reform.

“This report, if true, is one of the more shocking and distressing news stories we’ve seen, which is really saying something given the constant chaos and lies churned out by the Trump administration,” Rep. John Delaney, a Montgomery County Democrat said in a statement. “If this report is true, President Trump has undermined our fight against terrorism.”

Rep. Andy Harris of Baltimore County, the only Republican in the state’s congressional delegation, did not immediately respond to a request for comment.

Although it is not illegal for a president to reveal classified information, administration officials were reportedly so concerned that Trump’s disclosure would antagonize the foreign ally that provided the intelligence that White House aides quickly notified the CIA and the National Security Agency.

McMaster did say the discussion with the Russians included “threats to civil aviation.”

Before he faced reporters, the White House distributed statements from Secretary of State Rex Tillerson and Deputy National Security Adviser Dina Powell disputing the Post’s account.

Tillerson, like McMaster, said there was no discussion of “sources, methods or military operations.” The reports acknowledged as much but said the information Trump passed along to the Russians could allow them to deduce such sensitive matters.

Powell, who also participated in the meeting, flatly called the report “false.”

“The president only discussed the common threats that both countries faced,” she said.

The Russian officials visited the day after Trump fired Comey amid the ongoing U.S. investigation into the Trump campaign’s possible links to Russian interference in the 2016 presidential election.

A disclosure like that attributed to Trump would be illegal from anyone other than the president. But Sen. Richard Blumenthal, a Democrat from Connecticut, said, “No one is above the rule of law in this country.”

“It is absolutely terrifying,” Blumenthal said. “It’s another example of the free press uncovering stuff that the American people should know that hopefully will cause an outcry and outrage that will have some cumulative effect in protecting our democracy.”

Other senators offered sharp reactions to the reports, calling the president’s action, if true, “terrifying,” “reckless” and “deeply disturbing.” The Post’s report came just as senators were arriving for an evening vote.

Sen. Richard J. Durbin, a Democrat of Illinois, the assistant minority leader, said such a disclosure “may not only jeopardize our troops and our people, but the security of those who risk their lives to tell us what is actually happening.”

“If true, deeply disturbing,” tweeted Sen. John McCain of Arizona, the Republican who heads the Senate Armed Services Committee.

Sen. Lindsey Graham of South Carolina, echoed McCain, saying of the report, “If it’s true, it’d be troubling.”

Graham, reflecting the exasperation of many Republicans at being forced to respond to repeated Trump controversies, added, “I’m not going to speculate. I’m tired of speculating about Trump every five minutes.”

House Minority Leader Nancy Pelosi of San Francisco called for a full briefing for Congress on the extent of the potential damage done.

“Even if President Trump unwittingly blew a highly classified code-word source to the Russians, that would be dangerous enough. If the president outed a highly classified code-word source intentionally, that would be even more dangerous,” she said.

michael.memoli@latimes.com

lisa.mascaro@latimes.com

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Baltimore Sun reporter John Fritze contributed to this article.