The young man was discovered in a supermarket trolley abandoned on a main street in the north-western French town of Bruz, near Rennes in Brittany at around 7am on Tuesday morning. When emergency services arrived, the victim was in a critical state and was immediately rushed to hospital.
According to French regional Ouest-France, preliminary reports suggested he had been stabbed, tortured, raped and badly beaten.
He remains in a serious condition in hospital, the newspaper reported.
Later that morning, police arrested three men, two of whom are youths, in an apartment close to the town of Bruz, on suspicion of being the "perpetrators of the attack", according to Rennes public prosecutor Thierry Pocquet du Haut-Jussé.
Five others including two women were arrested on suspicion of being complicit in the attack and for allegedly "failing to assist a person in danger", which is considered a serious crime in France.
The savage attack in the town of 18,000 inhabitants appears to have been a "crime of revenge", Pocquet du Haut-Juseé told French daily Le Parisien on Thursday.
All eight suspects were due to appear before the investigating judge on Thursday.