Bernard Madoff, the man accused of masterminding a $US50 billion ($A73.5 billion) investment fraud, is under round-the-clock house arrest.

Bernard Madoff, the man accused of masterminding a $US50 billion ($A73.5 billion) investment fraud, is under round-the-clock house arrest.He's holed up in his $US7 million New York City apartment after prosecutors warned of his "harm or flight".Madoff, 70, has been subject to electronic monitoring and a 7 pm curfew under a December 17 court order. Now he is barred from leaving his Upper East Side apartment except for court appearances, and his building will be watched by security guards and video surveillance, according to a letter from prosecutors filed in federal court in Manhattan on Friday night Australian time. "The bail conditions are what the government has agreed to," Madoff's lawyer Ira Sorkin said.
He wouldn't say whether Madoff had been threatened.

Madoff was arrested earlier this month after telling his two sons and federal investigators that he had been using money from new investors to pay off old ones in a massive Ponzi scheme.

He said clients of New York-based Bernard L. Madoff Investment Securities LLC lost $US50 billion. The security service, which was put into place on the weekend, will watch Madoff's doors and will be able to send a signal from an observation post to the Federal Bureau of Investigation, according to the letter. One reason for the new bail conditions was "to prevent harm or flight," the government said. The New York Daily News last week quoted an unnamed source saying that Madoff and his family had been threatened if he didn't repay investors. Other bail conditions remain. Madoff posted a $US10 million bond, guaranteed by his wife and brother Peter, and he and his wife have agreed to surrender homes in Manhattan, Montauk, New York, and Palm Beach, Florida, if he flees. Madoff remains subject to electronic monitoring.
The Manhattan apartment is worth about $US7 million, according to bail papers.
Ruth Madoff, who hasn't been accused of wrongdoing, also has surrendered her passport. Madoff, who hasn't formally responded to charges against him, is due to return to court on January 12.