A former FBI informant charged with making up a multimillion-dollar bribery scheme involving President Joe Biden, his son Hunter and a Ukrainian energy company had contacts with officials affiliated with Russian intelligence, prosecutors said in a court paper Tuesday.

Prosecutors revealed the alleged contact as they urged a judge to keep Alexander Smirnov behind bars while he awaits trial. He’s charged with falsely reporting to the FBI in June 2020 that executives associated with the Ukrainian energy company Burisma paid Hunter and Joe Biden $5 million each in 2015 or 2016. The claim has been central to the Republican impeachment inquiry in Congress.

Smirnov is due in court later Tuesday in Las Vegas. He has been in custody at a facility in rural Pahrump, about an hour drive west of Las Vegas, since his arrest last week at the airport while returning from overseas.

Defense attorneys David Chesnoff and Richard Schonfeld said in a statement ahead of the hearing that they were asking for Smirnov’s release while he awaits trial “so he can effectively fight the power of the government.”

Prosecutors said that during an interview before his arrest last week, Smirnov admitted that “officials associated with Russian intelligence were involved in passing a story” about Hunter Biden. They said Smirnov’s contacts with Russian officials were recent and extensive, and said Smirnov had planned to meet with one official during an upcoming overseas trip.

They said Smirnov has had numerous contacts with a person he described as the “son of a former high-ranking government official” and “someone with ties to a particular Russian intelligence service.” They said there is a serious risk that Smirnov could flee overseas to avoid facing trial.

The White House didn’t immediately comment on the claims in Tuesday’s court filing.

Prosecutors say Smirnov, who holds dual U.S.-Israeli citizenship, falsely reported to the FBI in June 2020 that executives associated with the Ukrainian energy company Burisma paid Hunter and Joe Biden $5 million each in 2015 or 2016.

Smirnov in fact had only routine business dealings with the company starting in 2017 and made the bribery allegations after he “expressed bias” against Joe Biden while he was a presidential candidate, prosecutors said in court documents. He is charged with making a false statement and creating a false and fictitious record. The charges were filed in Los Angeles, where he lived for 16 years before relocating to Las Vegas two years ago.

Smirnov's claims have been central to the Republican effort in Congress to investigate the president and his family, and helped spark what is now a House impeachment inquiry into Biden. Democrats called for an end to the probe after the indictment came down last week, while Republicans distanced the inquiry from Smirnov’s claims and said they would continue to “follow the facts.”

Hunter Biden is expected to give a deposition next week.

The Burisma allegations became a flashpoint in Congress as Republicans pursuing investigations of President Biden and his family demanded the FBI release the unredacted form documenting the allegations. They acknowledged they couldn’t confirm if the allegations were true.

Hunter Biden’s lawyers say Smirnov's claims may have tainted the case against the president’s son.

The gun and tax charges against Hunter Biden are separate from the claims made by the informant, but his attorneys say the chatter over the informant contributed to the collapse of the plea deal offered to the president's son last summer.

The filing comes as Hunter Biden continues his public offensive over claims about his professional life and drug use that have been central to congressional investigations and an impeachment inquiry that seeks to tie his business dealings to his father.

The president’s son is charged with lying on a form about his drug use to buy a gun in 2018. He has pleaded not guilty, and his lawyers say one photo that prosecutors used as evidence of cocaine use was actually a photo of sawdust sent by his therapist to encourage him to stay clean.

The Justice Department special counsel overseeing the case against him also filed the charges against Smirnov last week. He is accused of falsely reporting to the FBI in June 2020 that executives associated with the Ukrainian energy company Burisma paid Hunter and Joe Biden $5 million each in 2015 or 2016.

But before that case was filed, the prosecution followed the informant “down his rabbit hole of lies,” defense attorneys said in court documents. The special counsel's office started investigating Smirnov's claims three years after he originally reported them to his handler, in July 2023. The plea deal imploded around the same time, after prosecutors indicated that an investigation into bribery allegations remained open, defense attorneys said in court documents.

A spokesperson for special counsel David Weiss declined to comment. Prosecutors have previously said that the evidence against Hunter Biden is “overwhelming,” including cocaine residue found on the pouch used to hold his gun, and rejected the defense contention that the charges were politically motivated.

Hunter Biden is also charged in Los Angeles, accused of failing to pay $1.4 million in taxes while living an “extravagant lifestyle.” Both cases stem from the time when he acknowledged being addicted to drugs.

The cases were filed by special counsel David Weiss, who also charged Smirnov with lying to the FBI in an indictment filed last week. Smirnov's defense attorneys are pressing for his release from custody.

The charges against Hunter Biden were filed after the collapse of a plea deal that would have avoided the possibility of a trial while his father is campaigning for another term as president. The deal imploded, though, during a hearing in July, around the same time prosecutors from the special counsel’s office started looking into the informant’s claims at the request of the FBI, according to court documents.