Anti-apartheid activist Winnie Madikizela-Mandela, wife to Nelson Mandela during his decades of imprisonment, died on Monday, a family spokesman said. She was 81.

Madikizela-Mandela died peacefully surrounded by her family following a long illness that had kept her in and out of hospital since the start of the year, Victor Dlamini said in a statement.

“She fought valiantly against the apartheid state and sacrificed her life for the freedom of the country,” the statement said.

“She kept the memory of her imprisoned husband Nelson Mandela alive during his years on Robben Island and helped give the struggle for justice in South Africa one its most recognisable faces.”

Madikizela-Mandela was jailed several times for her part in the fight against white-minority rule and she campaigned for the release of her husband at home and abroad.

But her marriage to Mandela began to fall apart in the years after he was released from prison in 1990. The couple divorced in 1996, nearly four decades after they were married. They had two children together.