The New York Democrat congressman, a once-rising star who also ran for mayor, was convicted of having illicit online contact with a 15-year-old North Carolina girl in 2017.

He began serving a 21-month prison sentence that November at the Federal Medical Center Devens, located about 64 kilometres west of Boston in Ayer, Massachusetts.

The Federal Bureau of Prisons website now shows Weiner is in the custody of its Residential Re-entry Management office in Brooklyn, New York.

It's not immediately clear when he was transferred and where he's currently staying. Emails were sent to the bureau, federal court in New York and Weiner's lawyer requesting comment.

The bureau website shows Weiner is slated to complete his sentence on May 14.

Weiner will have to register as a sex-offender and spend three years on supervised release under the terms of his sentence.

At his sentencing, he said he'd been a "very sick man for a very long time" because of his sex addiction.

Weiner's attorney said the ex-lawmaker likely exchanged thousands of messages with hundreds of women over the years and was communicating with up to 19 women when he encountered the teenager.

Australian Associated Press