The shooting occurred at a railway station in La Plata where fans were waiting to board a train to Quilmes on the outskirts of Buenos Aires for the match between Estudiantes and Argentinos Juniors in the Clausura championship.
At least two other people were hurt in the attack and a number of arrests were made and firearms confiscated, an official with the secretariat for security at football matches told La Nacion's website.
The South American champions went down to a goal by 39-year-old former Estudiantes forward Jose Luis Calderon, who retired in November after differences with coach Alex Sabella only to be persuaded to play on for the rest of the season by Argentinos' Claudio Borghi.
On the night Real Madrid's Gonzalo Higuain scored for Argentina in their 1-0 friendly win over Germany, his brother Federico helped Godoy Cruz beat Lanus 2-1 to take the sole lead in the standings.
Striker Santiago Salcedo equalised in the 57th for Lanus but midfielder Carlos Sanchez scored the winner with 17 minutes remaining after Federico Higuain's shot came back off keeper Agustin Marchesin.
