A 16-year-old girl was gang-raped and had her eyes gouged out by her older sister to free her from demons, Argentinian police say.

The girl is reportedly clinging to life in hospital in the town of General Pinedo.

Her older sister, 22, is the only one charged in the gruesome exorcism ritual so far.

Police said she told her parents she was worried about bizarre visions her little sister had been having.

"The girl said that she was possessed by a demon and evil beings, saw bugs and animals (that weren't there)," police commissioner Paul Almiron told Buenos Aires newspaper the Cronica. "So the parents went to seek help from (the pastor)."

Almiron said the pastor told the family to cut her eyes out to exorcise the demons.

It's unknown if the alleged gang rape that apparently took place beforehand was part of the ritual, but police say rape charges are pending.

Local media have published gruesome photos of the teen in hospital. Police said it appears the older sister used a sharp instrument for the terrible deed.

The teen is also suffering from severe injuries in her genital area.

Spanish online portal Terra reported police found a Bible covered in blood and pieces of the girl's eyes at her home, the scene of the crime.

"It is the first time in 22 years of policing that I've seen something like this," Almiron told the Cronica, adding the attack is "very hard to explain."