Paul Manafort, the imprisoned former campaign manager for Donald Trump, has been hospitalized, his lawyer said Tuesday.

"His family and friends are extremely concerned about his health and still do not have a full understanding of his medical condition or well-being," said Manafort's lawyer, Todd Blanche.

Blanche said Manafort has been hospitalized since last Thursday but is reported to be stable.

Manafort, 70, has been locked up at Federal Correctional Institution Loretto in Loretto, Pennsylvania, where he's serving a seven-and-a-half year sentence.

The longtime GOP operative was charged by special counsel Robert Mueller's office with several crimes, including tax evasion and violating federal lobbying laws by concealing millions of dollars he earned representing pro-Russian political figures in Ukraine. Manafort was convicted after a jury trial in Alexandria, Virginia and pleaded guilty to related charges in a separate case in Washington, DC.

Before he was sentenced earlier this year, Manafort's lawyers told the court he was suffering from severe gout. But the lawyers did not report any other serious medical conditions.

In his statement, Blanche expressed frustration over the lack of detailed information released by the federal Bureau of Prisons.

"Regrettably, the Bureau of Prisons refused to provide any information to his family or me about Mr. Manafort’s condition or whereabouts, apart from stating he was 'safe,' citing privacy and safety concerns," Blanche said.

The Bureau of Prisons released a brief statement Tuesday afternoon. "For safety and security and privacy reasons, we cannot provide specific information about an inmate's medical condition," it said.