A police officer can be seen on an Associated Press video firing what appeared to be a live pistol round at anti-World Cup protesters Sunday near Rio de Janeiro's Maracana soccer stadium.
During the small but violent and chaotic protest that played out about 1.5 kilometers (1 mile) from the stadium, another man in plainclothes who identified himself as a police officer also pulled a pistol and fired two shots into the air.
Pedro Dantas, a spokesman for the Rio de Janeiro security secretariat that oversees all security forces, said in a phone interview that if authorities verify the accuracy of the video, "we'll immediately open an investigation into the incident."
In a later emailed statement, the secretariat said riot police were hit by Molotov cocktails thrown by protesters. The statement didn't indicate if any officers were hurt.
The action took place around the beginning of the soccer game between Argentina and Bosnia-Herzegovina -- the first World Cup match played in Maracana stadium since 1950.
"We're seeing tonight the same police brutality we've seen during the past year, and that's why we have to keep protesting," said Karen Rodrigues, a 23-year-old student at the demonstration that drew around 200 people.
Another protest occurred in the capital, Brasilia, but drew only a handful of participants, and a small protest also was held in Porto Alegre.
Mass protests broke out across Brazil during last year's Confederations Cup soccer tournament, the warm-up to FIFA's premier event. At that time, more than 1 million Brazilians took to the streets on a single day in the largest demonstrations this South American nation had seen in a generation.
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Video Credit: Associated Press