A US federal judge has ordered the US Capitol siege rioter known as the "QAnon shaman", who allegedly left an ominous note for Vice-President Mike Pence, to be detained pending trial, saying he participated in a "violent insurrection".

At the US District Court in Phoenix, Arizona, Judge Deborah Fine ruled that Jacob Chansley, who was photographed inside the US Senate Chamber wearing horns during the Capitol riots, should not be released from custody.

The Navy veteran and QAnon follower allegedly left a note for Mr Pence warning: "It's only a matter of time, justice is coming."

QAnon is a conspiracy theory that casts US President Donald Trump as a saviour figure and elite Democrats as a cabal of Satanist paedophiles and cannibals.

Judge Fine called Mr Chansley "an active participant in a violent insurrection that attempted to overthrow the United States Government" and said she feared he was a danger to the community and a flight risk.

As she made her ruling on Friday local time, Mr Chansley interjected and tried to speak, but the judge cut him off, saying he should avoid making statements.

Prosecutors have no 'direct evidence' of assassination plot

Her ruling came shortly after prosecutors in Arizona walked back sweeping statements they made just a day earlier, claiming the Government had "strong evidence" that the "intent of the Capitol rioters was to capture and assassinate elected officials in the United States Government".

The top federal prosecutor overseeing the sweeping probe of the riots at the Capitol told reporters that at this stage, they had no "direct evidence" that rioters who stormed the US Capitol had formed "kill-capture teams".

The criminal case against Mr Chansley is just one of a growing number, as investigators in Washington DC scour more than 140,000 videos and photos from the Capitol siege.

As of Friday morning, Michael Sherwin, acting US attorney for the District of Columbia, said his office had brought 98 criminal prosecutions so far and opened investigations into more than 275 people in connection with the Capitol riots, in which Mr Trump's supporters stormed the building, ransacked offices and in some cases, attacked police.

Court filings in the cases suggested some of the rioters came prepared with weapons, gas masks, ballistic vests and zip ties.

The people charged included a retired firefighter who reportedly hurled a fire extinguisher at police, a man accused of attacking police with a flag pole and another suspect who officials said was caught with explosives and firearms in his truck near the Capitol building.

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The FBI is also looking for suspects in connection with the death of Capitol police officer Brian Sicknick.

Steven D'Antuono, assistant director in charge of the FBI's Washington Field Office, urged suspects to turn themselves in.

"To those of you who took part in the violence, here's something you should know: Every FBI field office in the country is looking for you," he said.

"As a matter of fact, even your friends and family are tipping us off."

Reuters