A 21-year-old Iraqi man was rushed to hospital from a migrant processing center in the northern Greek region of Imathia on Wednesday night with what doctors suspect are knife wounds to his back.
The young man was injured in an altercation with another camp resident, a 48-year-old Syrian man, who has been arrested.
Police said the argument was sparked by personal differences between the two men.
In a related development, a livestock farmer on the eastern Aegean island of Lesvos on Wednesday opened fire against a group of migrants he claims were trying to steal his sheep.
The incident took place near the refugee processing center of Moria, where thousands of migrants and asylum-seekers are crammed together in squalid conditions.
No injuries were reported in the incident.