The former US First Lady Rosalynn Carter, the wife of ex-President Jimmy Carter, has died at the age of 96.

The Carter Center confirmed in a statement that she died peacefully with her family by her side.

On Friday, it was reported that she had entered a hospice care home in the state of Georgia, and was spending time with her 99-year-old husband, who has been in hospice care since February.

Mrs Carter was diagnosed with dementia in May.

The longest-married first couple marked their 77th wedding anniversary in July.

Mrs Carter was born Eleanor Rosalynn Smith on 18 August 1927.

She married President Carter on 7 July 1946, and they went on to have four children.

When her husband began his political career in the 60s - first as Georgia state senator, governor, and later president - Mrs Carter was focused on raising mental health awareness and reducing the stigma attached to people with mental illnesses.

As first lady of Georgia she was a member of a governor's commission to improve services for the mentally ill, and as the US First Lady she became honorary chair of the President's Commission on Mental Health, which was key to passage of a 1980 act that helped fund local mental health centres.

After leaving Washington she and her husband founded the Carter Center 1982, through which she continued her advocacy work for mental health, early childhood immunisation, human rights, conflict resolution and the empowerment of urban communities.

In a 2013 interview with C-SPAN, she said: "I hope our legacy continues, more than just as first lady, because the Carter Center has been an integral part of our lives.

"And our motto is waging peace, fighting disease and building hope.

"And I hope that I have contributed something to mental health issues and help improve a little bit the lives of people living with mental illnesses."