An investigation is being opened into the killing of a 24-year-old prisoner in New Caledonia's main jail, presumed to be beaten to death by his five fellow cell inmates.
The young man, who was said to be serving a short sentence, was found by prison guards.
The incident has been reported by the union of corrections officers which has repeatedly denounced the overcrowding at the Camp Est prison.
The union leader says given the poor conditions it was inevitable that such an incident would occur.
He says they will ask for reinforcements in the cell block because of fears of further violence in response to the killing.
In August, the French president, Nicolas Sarkozy, promised that a new prison would be built to replace Camp Est which dates back to the 19th century.