One of the most bizarre bouts we've found from South America was a 2011 clash between Alfredo Brigido Ruiz Diaz (then 5-3, 2) and Aldo Federico Maciel (then 3-2, 3). This all Argentinian bout was held in Maciel's home town of Formasa and fought at the the Formasa Estadio del Bicentenario (not to be confused with the beautiful Estadio San Juan del Bicentenario).
What seemed like a bout between 2 pretty poor level Argentinian sluggers ended up in what could only be termed a brawl but not between the two fighters who ended up standing next to each other as the fans took over the ring, threw plastic chairs at each other and generally acted like thugs. This forced the referee to call off the contest in the 6th round and call a no contest, likely saving Maciel from a loss.
Sadly since this bout Maciel hasn't fought again and Diaz has gone 1-1-2 (he returns at the weekend to face Icho Larenas).
The video below is thanks to FormosaDeportiva and shows some of the action and the very peculiar ending