The US Attorney General accused 3 members of a right-wing militia of plotting to storm the Capitol Building (Congress), with the aim of preventing the confirmation of President Joe Biden's victory, while a congressional police official called for increased security of the building.

The three members belong to what is known as "loyal to the oath," classified as an extreme right-wing organization.

On Thursday, Acting Congressional Police Commander Yujananda Bateman urged lawmakers to add permanent fencing and backup security personnel to the Capitol building after the deadly January 6 attack.

"I can say unequivocally that significant improvements must be made to the physical security infrastructure to include a permanent fence, and there should be standby forces in place in the vicinity of the Capitol," Bateman said.

"We will not accept the deployment of additional forces or the construction of a permanent fence as this is a long-term force in the capital," Washington Mayor Muriel Bowser wrote on Twitter, but said that "potential volatile events" would require temporary additional insurance.

A Department of Homeland Security bulletin released on Wednesday did not contain specific threats, but indicated that some "violent domestic extremists" may find the Capitol incident a source of inspiration and encouragement.

Pelosi said that members of Congress want to carry weapons inside it and threaten to use violence (Reuters)

House Speaker Nancy Pelosi also said on Thursday that lawmakers would likely need to increase funding for security measures, because "the enemy is in the House," following a warning issued by the Department of Homeland Security about increasing threats.

In response to a question about what she meant by the term "the enemy within," Pelosi said, "This means that we have members of Congress who want to carry weapons inside it and threaten to use violence with other members of Congress."

Last week, a hidden pistol was found in the possession of Republican Representative Andy Harris while trying to enter the House of Representatives.

The Senate is preparing for the second trial of former President Donald Trump, on charges of incitement to revolt when he delivered a speech on January 6, after which hundreds of his supporters stormed the Congress building in an attempt to prevent the confirmation of President Joe Biden's victory in the elections.

On Thursday, more than 30 members of Congress signed a letter calling for increased protection in their regions, highlighting the increase in threats facing members in recent years, with Capitol Police investigating 4,894 threats in 2018, compared to 902 threats in 2016.

Since the attack, Congress has taken tight security measures, after entering the purpose of the visit was easy for the public compared to other institutions in Washington, such as the White House.

Before Biden's inauguration on January 20, a 2.4-meter-high fence was erected around the Capitol building, more than 20,000 National Guard troops were pushed into Washington, and thousands of soldiers are expected to remain in the capital until March.

Some lawmakers are outraged by the intensified security measures, such as installing a metal detector through which members of the House of Representatives pass.