WASHINGTON - The FBI privately warned law enforcement agencies Monday that far-right extremists have discussed posing as National Guard members in Washington and that others have reviewed maps of vulnerable spots in the city - signs of potential efforts to disrupt Wednesday's inauguration, according to an intelligence report obtained by The Washington Post.

The document, a summary of threats that the FBI identified in a Monday intelligence briefing, warned that "lone wolves" and adherents of the QAnon conspiracy theory, some of whom participated in the violent siege on the Capitol on Jan. 6, have indicated that they plan to come to Washington for President-elect Joe Biden's swearing-in ceremony.

The FBI also said it had observed people downloading and sharing maps of sensitive locations in Washington and discussing how those facilities could be used to interfere in security during the inauguration.

But the intelligence briefing did not identify specific plots to attack the inaugural events that would be akin to the Jan. 6 siege on the Capitol, and it noted that "numerous" militia and extremist groups are publicly denouncing potential violence against at the transition of presidential power.

While the FBI has picked up "suspicious traffic" in monitoring the kinds of communication systems used by some participants in the Capitol siege, it includes "nothing that points to any specific action."

The FBI on Monday declined to characterize the credibility or gravity of the threats it outlined for law enforcement before the inauguration.

The agency instead pointed to remarks FBI Director Christopher Wray made last week, when he said the agents were monitoring an "extensive amount of concerning online chatter" and noted the challenge of "trying to distinguish what's aspirational versus what's intentional."

"We're monitoring all incoming leads, whether they're calls for armed protest, potential threats that grow out of the January 6 breach of the Capitol, or other kinds of potential threats leading up to inaugural events and in various other targets.

So we're latched up with all of our partners in that regard," Wray added.

A spokesman for the Secret Service also declined to comment on the threat report, or to characterize the agency's level of concern.

"The U.S. Secret Service takes all threats seriously and will continue to work with our federal, state, local and military partners to continue securing the 59th Inauguration based on the relevant intelligence available to the security community," said spokesman Justine Whelan.

The Post is withholding some details outlined in the intelligence report at the request of the FBI to avoid revealing intelligence-gathering methods and specific security vulnerabilities.

The Secret Service is responsible for coordinating all security for the inauguration, which is categorized as a national security special event. The FBI is responsible for gathering intelligence on threats surrounding the event and managing any crises that develop.

After the Capitol attack, the FBI has scrutinized members of extremist groups such as the Oath Keepers, the Three Percenters and the Proud Boys, a male-chauvinist group with ties to white nationalism, making numerous arrests in recent days.

The FBI's intelligence briefing comes amid worry across the country about potential threats to Biden's inauguration and an unprecedented military lockdown of the District of Columbia's downtown and the National Mall.

At least 21,500 National Guard troops, thousands more law enforcement officers and miles of temporary fencing have been brought into the city to cordon off the iconic monuments and historic buildings that normally serve as the backdrop for a peaceful transfer of power between presidential administrations.

In its intelligence briefing, the FBI described the chatter it has been monitoring of groups associated with the Jan. 6 attack, particularly QAnon, whose adherents were prominent participants in the siege.

People affiliated with the baseless conspiracy theory, which claims that Trump is fighting against a cabal that traffics children, have shown interest in infiltrating security checkpoints at the inauguration, according to the report.

"QAnon members have discussed posing as National Guard soldiers, believing that it would be easy for them to infiltrate secure areas," according to the document, which added that members have been crowdsourcing images to surveil the security perimeter.

The FBI also said individual figures who have no clear ties to specific groups but have protested the election results have shown interest in the event.

"Concerns of lone wolf actors are increasing," according to the report, which noted that five people who took part in an armed demonstration at the Ohio Capitol on Sunday have said they were traveling to Washington for the inauguration.

The FBI has also observed an increase in surveillance of law enforcement's security preparations for the inauguration. According to the report, National Guard troops have reported seeing several individuals photographing and recording their work. Some of those videos have been uploaded online, the FBI report said.

The intelligence briefing also noted reports of unknown individuals accessing camera footage of secured areas where public access is prohibited.

It is unclear whether such efforts are the work of individuals aiming to disrupt the inauguration or curious passersby documenting the fortress that has sprung up.

The metamorphosis of the nation's capital into a veritable Green Zone is part of an aggressive effort by law enforcement to prevent more violence after the siege on the Capitol by an armed and violent pro-Trump mob.

Thousands of demonstrators that day came to Washington for a rally and other protests. Then, encouraged by Trump, they marched on the Capitol and fought through police barricades to break into the building and stop Congress's certification of the election results. Five people died in the riot, including one Capitol Police officer.

That attack - the first time the Capitol has been overrun since the War of 1812 - has led to perhaps the tightest security of any of the previous 58 presidential inaugurations.

When Supreme Court Justice John Roberts swears in Biden, there will be no sea of spectators filling the National Mall and no waving crowds lining a motorcade route along Pennsylvania Avenue that presidents normally take from the Capitol to their new home for the next four years.

To avoid line of sight of the Capitol balcony, where the ceremony takes place, barricades have walled off the National Mall and adjoining streets. Many residents of the historic rowhouses in neighboring Capitol Hill, just east of the Capitol, have to go through police checkpoints to leave and return to their homes.