"Ten Chadian nationals were shot dead in cold blood in Sbeha by a group of armed men, all of them wearing military uniforms," the ministry said in a statement.
It added that the attackers were all Libyan and described the incident as "an odious crime perpetrated against innocent civilians".
The circumstances of the incident were not immediately clear but N'Djamena said the Chadians were on their way home to Chad from the Libyan capital Tripoli.
Migrants are chronically attacked by armed gangs prowling Libya's lawless desert south.
Thousands of sub-Saharan Africans have for decades sought employment in oil-rich Libya but many returned home after Moamer Kadhafi was slain in 2011.