Sick sadists are stalking fields and mutilating horse genitals in what is feared to be satanic rituals.
Animal rights activists believe a twisted beast is ritualistically cutting the right ears off of the horses and removing their organs.
Increasing numbers of the gruesome killings have been reported at farms across France.
And there are fears the trend is spreading with cases reported in the UK, US, Germany, Belgium and Spain.
Detectives are under increasing pressure from animal lovers to solve the grisly crimes.
Freaks are reported to be lassoing horses, removing their ears, genitals and eyes, before leaving their mutilated corpses behind.
Milene Cornic, part of the La Ligue des Animaux group in France, said she believes it to be the work of satan worshippers.
She said: “We believe they could be satanic rituals. We find it hard to believe that there could be another reason.
“These appear to be organised people. It can’t be the actions of a single person.
“Because there are incidents that take place close together in different regions in France. So I think that’s clear.”
The satanic ritual theory is one the police are investigating.
French police have released a sketch of one suspect who was spotted attacking a horse before turning on its owner.
Nicolas Demajaen runs a horse refuge in France where two of his ponies were lacerated.
And he himself was so badly wounded by the sick knifeman he was rushed to hospital.
He said: “There are no words. It is barbarism, cruelty. And a gratuitous act because these animals cannot defend themselves.”
Last weekend, two mares were attacked and left with “serious injuries to genitals” in Jura.
And Puy-de-Dome, Moselle, Vendee, Aisne and Seine-Maritime have also had cases.
Earlier this month, a pony was found dead and mutilated in Essonne.
On August 8, an 18-month-old horse was attacked in Saone-et-Loire.
Its owner said it had had “one ear cut off and one eye torn out, the heart stabbed and the vagina removed.”
And the owner said the horses had been lassoed by the attackers.
The LLDDA have a petition online demanding the Interior Minister Gerald Darmanin create a crisis centre to coordinate the investigation.
In a note written in June, seen by French newspaper Le Parisien, the French Central Territorial Intelligence Service admits there is “a real desire to harm equines in general while keeping an ear as a trophy”.
The note also reportedly said: “Questions arise about the authors of these acts and their real intentions: superstition, fetishism, satanic ritual, sectarian or other.”
The attacks seem to be taken place closer and closer together and the authorities are under pressure to make arrests.