(Adds details of robberies, arrests)
By Angus MacSwan
PORTO ALEGRE, Brazil, June 25 (Reuters) - An Argentine fan in Brazil for the World Cup soccer tournament was shot in the leg during a bar fight, security officials said on Wednesday, stoking concerns about possible violence if Argentina meets Brazil in the championship match.
Six other Argentine fans were arrested for trying to steal tickets to their national team's match against Nigeria on Wednesday in Porto Alegre, the southernmost World Cup host city.
Tens of thousands of Argentines have flooded across Brazil's southern border this month, prompting increased security measures focused on Argentina's notorious hooligans. Brazil has already stopped more than 30 Argentines from entering the country due to their involvement with the violent "barras bravas" fan clubs in their national league.
The Argentine fan shot in the leg escaped serious injury and he was treated at an emergency room during Wednesday's pre-dawn hours, according to a public security spokesman. Argentina's state news agency Telam identified the injured fan as 35-year-old Gonzalo Nunez.
Both Argentina and Brazil finished at the top of their respective groups in the first round of the tournament, so their only possible faceoff would be in the World Cup final on July 13 at the storied Maracana Stadium in Rio de Janeiro. (Additional reporting by Brad Haynes in Sao Paulo and Anthony Boadle in Brasilia, editing by G Crosse)