Coroners have confirmed the body that was found in a bag and tied to an anchor at a depth of 1000 metres belonged to Olivia, 6, the older of the two sisters.

A similar bag that was empty was found nearby by a special oceanographic research vessel helping in the operation, Spain's Civil Guard said.

The search for Olivia's one-year-old sister Anna and their father, Tomas Gimeno, is ongoing.

National and regional government officials condemned Olivia's death and showed support for the girls' mother, Beatriz Zimmermann.

Spanish Prime Minister Pedro Sanchez tweeted: "I cannot imagine the pain of the mother of little Anna and Olivia.

"My hug, my love and that of my whole family, who today sympathises with Beatriz and her loved ones."

Women's rights organisations have called for protests across Spain against the recent surge in violence against women, often using children as a means of inflicting harm.

Gimeno and the girls went missing on April 27 on Tenerife, the largest island in the archipelago off West Africa.

Zimmermann, who is divorced from the girls' father, was allegedly told by him that she would never see the girls again.

Investigators launched a search on land and sea but narrowed in on the waters off Tenerife after Gimeno's boat was found empty and drifting at sea.

Australian Associated Press