Mary Richardson Kennedy, the 52-year-old estranged wife of Robert F Kennedy Jr, has died, her family has said, in what local media called an apparent suicide at her home in suburban New York.

"We deeply regret the death of our beloved sister Mary, whose radiant and creative spirit will be sorely missed by those who loved her," the Richardson family said in a statement sent to the AFP news agency by their lawyer on Wednesday.

The Journal News local newspaper and New York's Daily News quoted unidentified sources saying that Kennedy hanged herself.

Police in the town of Bedford, north of New York City, said only "a deceased individual had been located inside an out building on that property", referring to the family's address.

However, they would not immediately confirm the name.

Robert F Kennedy Jr is the son of Robert F Kennedy, who was shot dead in 1968 while seeking the Democratic nomination for the presidency previously held by his brother John F Kennedy, assassinated in 1963.

Mary Kennedy and her husband had been separated since 2010.

She was Kennedy Jr's second wife and they were married for 16 years, with four children.

Source: Agencies