In this photo taken on Sunday, April 21, 2013, Maria Butina, leader of a pro-gun organization in Russia, speaks to a crowd during a rally in support of legalizing the possession of handguns in Moscow, Russia.

A U.S. judge Wednesday ordered an alleged Russian agent to be jailed pending trial shortly after federal prosecutors warned in court filings that she posed an "extreme risk of flight."

Mariia Butina, 29, pleaded not guilty to charges of conspiring to act as an agent of a foreign government in Washington, D.C., district court.

During the same court proceeding, U.S. prosecutors revealed that there is a separate fraud investigation being conducted into an unidentified American who is referenced in prior court documents in Butina's case.

In court documents filed earlier on Wednesday, prosecutors also alleged that Butina, who said she was a gun-rights activist and developed ties to an "extensive network of U.S. persons in positions to influence political activities," offered to exchange sex for a job with an interest group.

The charges against Butina have exploded into a news cycle already thick with intrigue about ties between Vladimir Putin's Russia and U.S. political figures.

Last week, 12 Russian agents were indicted in special counsel Robert Mueller's probe into Moscow's interference in the 2016 election and possible links between President Donald Trump's campaign and the Kremlin. Trump, meanwhile, was forced to walk back a statement that indicated he accepted Putin's view that Russia didn't interfere in the election, which contradicts the findings of U.S. intelligence agencies. Butina's case isn't related to the Mueller investigation.

In arguing that Butina ought to be detained before trial, prosecutors said "her history of deceptive conduct" and "extensive foreign connections" posed the risk that she would flee the country beforehand.

Butina is charged with conspiring to act as an agent of a foreign government. She is accused of conspiring with Russian agents to infiltrate a U.S. gun rights organization as part of "a covert Russian influence operation."

An FBI special agent had previously described in court documents Butina's connections to an unnamed "high-level official in the Russian government," arguing that Butina had acted at the direction of that official.

Prosecutors revealed in the filing on Wednesday that Butina lived with a 56-year-old American, identified only as "U.S. Person 1," during her time in the U.S., although she appeared to "treat it as simply a necessary aspect of her activities" according to papers seized by the FBI.

Butina "complained about living with U.S. Person 1 and expressed disdain for continuing to cohabitate with U.S. Person 1," prosecutors say the seized papers show.

News outlets including The Washington Post have identified the unnamed person as Paul Erickson, a Republican activist and National Rifle Association member whose connections to Butina have been previously reported. Erickson is 56 years old, recent news reports show.

The filing also alleges that "on at least one occasion, Butina offered an individual other than U.S. Person 1 sex in exchange for a position within a special interest organization."

Prosecutors also say Butina had strong connections to a Russian billionaire with "deep ties to the Russian Presidential Administration." The unnamed oligarch, referred to in Butina's correspondence as her "funder," was "listed in Forbes as having a real-time net worth of $1.2 billion as of 2018," prosecutors said in the filing.