An elephant, labelled one of the "loneliest" in the world by animal rights activists, has passed away at a Philippines zoo, where she spent the majority of her life confined to a solitary enclosure.

An outpouring of tributes has emerged for Mali, who captivated audiences as Manila Zoo's star attraction for four decades and was deeply cherished.

Nonetheless, the solitary existence of the nation's only elephant remained a persistent source of concern for animal rights activists.

One such advocate was Sir Paul McCartney, who implored authorities to transfer Mali to an elephant sanctuary.

Mali's passing on Tuesday was announced in a Facebook video by Manila mayor Honey Lacuna, who cherished her childhood memories of visiting the zoo to see Mali.

On the preceding Friday, the Asian elephant was repeatedly seen rubbing her trunk against a wall, a sign of distress, according to the zoo's chief veterinarian, Dr. Heinrich Patrick Peña-Domingo.

By early Tuesday, Mali was lying on her side and experiencing laboured breathing. Veterinarians administered antihistamines and vitamins, but she succumbed to her ailments later that afternoon. An autopsy revealed cancerous tumours in some of her organs and a blockage in her aorta.

Mali, officially known as Vishwa Ma'ali, was gifted to former Philippine first lady Imelda Marcos by the Sri Lankan government in 1981 at 11 months old.

Manila Zoo also accommodated another elephant, Shiva, who arrived in 1977 and passed away in 1990. Since then, Mali remained the zoo's only elephant.

During the peak of the pandemic, Manila Zoo served as a vaccination site for children, where Mali's presence offered amusement.

Animal rights organizations condemned the substandard conditions at Manila Zoo and maintained that its keepers were ill-equipped to deliver proper medical care to Mali.

Zoo officials, however, contended that captivity was the most suitable option for Mali, given her lack of familiarity with life in the wild.