WASHINGTON • Federal prosecutors have offered an ominous new assessment of last week's siege of the United States Capitol by President Donald Trump's supporters, saying in a court filing that rioters intended "to capture and assassinate elected officials".

Prosecutors offered that view on Thursday in a filing asking a judge to detain Jacob Chansley, the Arizona man and QAnon conspiracy theorist who was famously photographed wearing horns as he stood at the desk of Vice-President Mike Pence in the chamber of the US Senate.

The detention memo, written by Justice Department lawyers in Arizona, goes into greater detail about the Federal Bureau of Investigation's probe into Chansley, revealing that he left a note for Mr Pence warning that "it's only a matter of time, justice is coming".

"Strong evidence, including Chansley's own words and actions at the Capitol, supports that the intent of the Capitol rioters was to capture and assassinate elected officials in the United States government," prosecutors wrote.

Chansley was due to appear in federal court yesterday.

The assessment comes as prosecutors and federal agents have begun bringing more serious charges tied to the violence at the Capitol.

These include revealing cases on Thursday against one man - retired firefighter Robert Sanford - on charges that he hurled a fire extinguisher at the head of a police officer, and another, Peter Stager, for beating a different officer with a pole bearing an American flag.

In Chansley's case, prosecutors said the charges "involve active participation in an insurrection attempting to violently overthrow the United States government", and warned that "the insurrection is still in progress" as law enforcement prepares for more demonstrations.

They also suggested that he suffers from drug abuse and mental illness, and told the judge he poses a serious flight risk.

"Chansley has spoken openly about his belief that he is an alien, a higher being, and he is here on Earth to ascend to another reality," they wrote.

The Justice Department has brought over 80 criminal cases in connection with the violent riots at the Capitol last week, in which Mr Trump's supporters stormed the building, ransacked offices and, in some cases, attacked police.

REUTERS