Michigan businessman Paul Whelan told reporters in a Russian courtroom Friday that he's being threatened, abused and harassed at Moscow's Lefortovo Detention Facility, and that his imprisonment on an espionage charge is akin to political kidnapping.

A judge extended the pretrial phase of Whelan's detention for three more months on Friday, which means Whelan, 49, of Novi is to remain in prison at least until Aug. 29.

“This is typical prisoner of war isolation technique," Whelan told journalists in the courtroom, the Associated Press reported. "They’re trying to run me down so that I will talk to them."

Whelan, an ex-Marine who was the director of global security for the Auburn Hills-based auto supplier BorgWarner, said he was in Russia in December for the wedding of a friend when he was arrested in his hotel and accused of spying.

He told the court on Friday that there was "absolutely no legitimacy" to the case against him, and said his imprisonment is retaliation for U.S. sanctions, BBC News reported.

The Russian Federal Security Service (FSB) alleges Whelan was caught in possession of a flash drive containing classified information. Whelan has told his lawyers that the flash drive came from a Russian friend, and that he was under the impression that it only contained photos of the friend's hometown.

Whelan, who was born in Canada to British parents and grew up in Ann Arbor, holds U.S., British, Canadian and Irish passports. If he's convicted of spying, he could be imprisoned for up to 20 years.

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“We of course remained concerned by the lack of evidence in his case and the secretary is committed to continuing to raise this at the highest levels,” said Morgan Ortagus, a State Department spokeswoman.

Paul Whelan's twin brother, David Whelan, told the Free Press that he believes his brother was targeted by Russian authorities because he was an American businessman.

"Unfortunately, the FSB appears to have miscalculated whatever result they helped to extort out of Paul's false arrest," he said. "Paul has shared notes through his lawyer that he believes his arrest has some sanctions-related element, but we don't know why he says that."

The continued detainment is an effort on the part of the FSB to "continue to string out the pretrial phase of Paul's case," David Whelan wrote in an email. "Unfortunately, there's no reason to think that their continued lack of evidence will free Paul. ... Paul is being wrongfully detained by Russian authorities. If there was any justice, Paul would be freed and sent home to his family."

Olga Karlova, an attorney on Paul Whelan's Russian legal team, told the Free Press that Whelan has been isolated in the Czarist-era prison.

"They aim to isolate Paul from the world as much as they can," she said. "We see it.

"We as his lawyers will do our best to keep his rights and interests. We are going to visit him next week and discuss our position."

Whelan told journalists in the courtroom Friday that he hasn't had access to books or mail in two months, and that he hasn't been permitted to take a shower in two weeks, BBC News reported.

Tanya Lokshina, a Moscow-based advocate for Human Rights Watch, said that although she is not familiar with the specific details of Whelan’s case, his statements in court suggest he is not being afforded the same rights as other Russian prisoners.

“Russian remand prisons have weekly showers as part of their regular routine," she said via email. "Not being able to shower for two weeks appears to be out of the ordinary. Foreign detainees should be treated no differently than Russian detainees."

During an April 30 meeting with Whelan in the prison, U.S. Ambassador to Russia Jon Huntsman Jr. was not allowed to read letters from Whelan's family, to ask him to sign a power of attorney, and was banned from "talking about anything that actually matters," said Andrea Kalan, a spokeswoman for the U.S. Embassy in Moscow, on Twitter.

David Whelan said his family is concerned that his brother has been interrogated without the presence of his lawyers or his translator.

“The mature, civilized course would be to let Paul go home to his elderly parents, who are wondering if they’ll see their son alive again,” Kalan tweeted on Friday, noting that there's "no evidence of any wrongdoing" in Whelan's case.

Contact Kristen Jordan Shamus: 313-222-5997 or kshamus@freepress.com. Follow her on Twitter @kristenshamus.