Vilma Espin, wife of Raul Castro, former rebel fighter and unofficial first lady of the country, died Monday after a long illness.

The 77-year-old wife of Cuba’s acting president Raul Castro, had disappeared from the public eye some years ago, generating rumors that she was ill. Official Cuban state television reported Monday that Espin had been suffering “a long illness.”

The Council of State declared an official day of mourning for “Cuba’s First Lady” starting Monday evening. Espin was cremated, as she wished, and will be buried during a private ceremony in Santiago de Cuba, her hometown.

According to the television report, the former revolutionary will be laid to rest in the memorial dedicated to revolutionaries in that part of Cuba who came to Fidel Castro’s help in his fight against dictator Fulgencio Batista.

Espin was a guerrilla fighter who helped Fidel and Raul Castro carry out the revolution. She and Raul Castro married in 1959 and had four children. Daughter Mariela Castro has followed in her mother’s footsteps and currently heads the Cuban National Center for Sex Education.

Espin was president of the Cuban Women’s Federation for 47 years, since its creation in 1960. She was also member of the State Council, the Politburo and the Central Committee of the Cuban Communist Party. Espin was a member of the National Popular Assembly, the Cuban Parliament, for 30 years.

Cuban flags will be lowered to half-mast at all public buildings and military bases Tuesday.