A man who took part in the storming of the US Capitol wearing a sweatshirt that said "Camp Auschwitz" is among a number of people arrested by the FBI over the assault, multiple media outlets reported on Tuesday. 

Robert Keith Parker appeared in a virtual hearing in the US District Court for the Eastern District of Virginia on charges of unlawful entry and violent entry and disorderly conduct. 

Details of his arrest were still under seal at the time of his court appearance and he was released on his own recognisance. 

Media outlets reported that Parker was the man shown in many photographs of last Wednesday's assault on the Capitol wearing a sweatshirt emblazoned with the words "Camp Auschwitz". 

The sweatshirt also bore a skull and cross bones and the words "Work Brings Freedom" - echoing the slogan in German over the gates at Auschwitz. 

As of Tuesday afternoon, the Justice Department had brought at least 70 cases in connection with the riot at the Capitol, in which five people died as supporters of President Donald Trump stormed the building, scaled walls, and ransacked offices. 

Many of those cases remain under seal, and a grand jury in Washington, D.C. has been convened to review possible charges. 

Many of those who have been arrested were captured on video and in photos, with some bragging about their actions. 

The FBI has been scouring more than 100,000 images and videos as it tries to track down suspects. 

Acting US Attorney for the District of Columbia Michael Sherwin said on Tuesday that while many of the people in custody were arrested on less serious charges, such as unlawful entry, he is expecting some offenders to face steeper charges. 

Among the possible charges some people could face include seditious conspiracy or felony murder in connection with the death of a Capitol Police officer. 

At least two other suspects tied to the events at the Capitol are due to make initial appearances in federal courts in New York on Wednesday, and another suspect who is already in custody for making threats towards House Speaker Nancy Pelosi and Washington, D.C. Mayor Muriel Bowser will appear in federal court in Washington for a detention hearing. 

It comes as US President Donald Trump urged his supporters not to launch new demonstrations as some are threatening with central Washington looking more and more like an armed camp ahead of the inauguration of Joe Biden as the next president. 

"In light of reports of more demonstrations, I urge that there must be NO violence, NO lawbreaking and NO vandalism of any kind," he said in a statement.

"That is not what I stand for, and it is not what America stands for. I call on ALL Americans to help ease tensions and calm tempers. Thank you."