MOSCOW (AP) — The firm managed by jailed U.S. investor Michael Calvey appealed to Russian President Vladimir Putin on Monday to take "personal control" of a fraud case against him and his colleagues.

Calvey and five colleagues were arrested this month on allegations of embezzlement involving a Russian bank where Calvey's firm, Baring Vostok, has a controlling stake. The arrest of Calvey, a well-known businessman who avoided talking politics and supported Russia's tech sector, has sent shockwaves through the Moscow business community.

"Our colleagues are accused of offences in connection with the execution of normal management functions at a commercial organization," Baring Vostok argued, adding that keeping them in pre-trial detention breaks the usual rules for such cases.

Asked if Putin was willing to take the case under his personal control, Kremlin spokesman Dmitry Peskov said he "wouldn't want to speculate."

Peskov added that Putin had not seen the letter but that he would be shown it. "It's a major case and it is under special control in the agencies that are investigating it," Peskov added.

Calvey's case has attracted influential supporters including Russia's business ombudsman, Boris Titov, and the CEO of a sovereign wealth fund, Kirill Dmitriev, who have asked officials to reconsider the decision to keep Calvey and others in jail pending trial. The U.S. embassy has complained it's not been given access to Calvey.

In a major address last week, Putin said businesses were often put under unnecessary pressure by Russian law enforcement. He has not addressed the Baring Vostok case directly.