The U.S. Federal Bureau of Investigation has warned of possible armed protests in Washington, D.C. and states in the days leading up to the inauguration of president-elect Joe Biden Jan. 20.

According to an FBI internal bulletin, "the bureau received information about an identified armed group intending to travel to Washington, D.C. Jan. 16...and warned that if Congress attempts to remove the president via the 25th Amendment a huge uprising will occur," The Deadline quoted a portion of the bulletin as saying.

Biden said he wasn't afraid of taking the oath outside" the Capitol building.

The riots at the U.S. Capitol last week have left the nation on edge. Three top Capitol security officials have resigned.

The Capitol Police is a 2,300-strong force of officers and civilians that protects politicians, staff and visitors. The department has an annual budget of around $515 million.

Politicians have demanded an evaluation of operations and a bureau briefing over what they called a "terror attack" that resulted in five deaths.

The National Guard has been given clearance to send up to 15,000 troops to Washington, D.C. and tourists have been restricted from visiting the Washington Monument until Jan. 24.

National Guard director Gen. Daniel Hokanson expects around 10,000 troops to be deployed in Washington, D.C. by Saturday.

Senator Chris Murphy said it wasn't clear if the National Guard would be enough to safeguard the country's capital and active duty troops may be deployed, too.

Prosecutors have filed more than a dozen criminal actions in federal courts for offenses ranging from attacking police officers, trespassing, stealing federal property and threatening members of Congress.