A visiting Belgrano player was hit in the face by a truncheon as riot police tried to control rioting fans near the end of his team's 2-0 defeat at Newell's Old Boys in Rosario, Argentinian media reported.
The defender Gaston Turus intervened as Belgrano players attempted to calm their supporters who were fighting with home fans at the Marcelo Bielsa stadium in Rosario, 300km north-west of Buenos Aires, in Friday night's match.
"The cops bashed me," Turus, who lay on the ground for two minutes after being struck and needed treatment to a deep cut below his left eye, was quoted as saying by La Nación. His team-mate Luciano Lollo was shown a red card for allegedly attacking a policeman.
After an interruption of nearly 10 minutes the match resumed and Maximiliano Urruti scored Newell's second goal in the ninth minute of added time. The Argentina striker Ignacio Scocco had put the home side ahead in the first half.
Fighting among supporters continued outside the stadium afterwards in the streets of Rosario, a hotbed of fan violence this year. A friendly between the city's two big rivals, Newell's and Rosario Central, relegated to the second-tier Primera B Nacional championship in 2010, was called off in January due to bomb attacks on the premises of both clubs.
As a result of another violent incident in Buenos Aires, the death of a man after a fight between rival gangs of Tigre supporters last week, their team's home match against All Boys on Sunday will be played behind closed doors.