The fight reportedly broke out after the Malian migrant suffered a psychotic episode, became violent and tried to steal from fellow seasonal workers in the vast tent camp in San Ferdinando, which sits on the outskirts of the southern city of Rosarno.
The overcrowded and dirty tent camp houses thousands of people who scrabble to get work largely in the area's orange groves.
Two policemen intervened, but called for back-up when they failed to calm the Malian. When he saw extra police arrive he lashed out with the knife, wounding one of the officers near the eye, the Corriere della Sera said.
Shocked and angry migrants then circled the officers, who drew their weapons and called for more back-up. The situation calmed down after several hours when police in riot gear arrived, but tension remained in the camp, the report said.
Dozens of migrants were taken to the local police station for interviews.
Rosarno is notorious in Italy for the climate of tension between its seasonal workers -- many of whom hail from sub-Saharan Africa -- security forces and local residents, and has been the scene of repeated clashes.