Bernard Madoff, convicted of swindling $65 billion through the biggest-ever Ponzi scheme, has told fellow prison inmates that he is dying of cancer, the New York Post reported on Monday, citing unnamed prison sources.

Madoff, 71, who since June has been serving a 150-year sentence at a North Carolina federal prison, has been telling fellow inmates he does not have much longer to live, the Post said, citing the unofficial and unusual sources.

The Post said there had been speculation that Madoff was suffering from pancreatic cancer earlier this year. Inmates said Madoff was taking about 20 pills a day and not doing very well.

The Post said Madoff's lawyer did not return messages Sunday and had previously declined to answer questions about whether Madoff had cancer. Reuters could not reach Madoff lawyer Ira Sorkin immediately for comment.

The tabloid also reported Madoff has engaged in a number of surprising new activities with some unexpected social circles.

A shirtless Madoff has joined weekly Native American religious purification ceremonies that involve prayers, heated rocks to induce sweat and smoking from a ceremonial pipe, the paper said.

The paper also reported that various gangs at the prison are trying to recruit Madoff while some inmates regularly cook sandwich wraps for him at their cells.

(Reporting by Joseph A. Giannone, editing by Maureen Bavdek)