SAO PAULO (AP) — Authorities in Rio de Janeiro said that about 50 Flamengo fans were detained on Wednesday after they set off firecrackers outside a hotel being used by Argentine club Independiente.
The two teams will play later Wednesday in the second leg of the Copa Sudamericana final at the Maracana Stadium.
The Copa Sudamericana is the continent's second most prestigious club competition after the Copa Libertadores. Independiente won the first leg 2-1 last week.
Police used tear gas to bring the crowd under control in the early hours, while further incidents involving rival supporters followed later in the day. About 10,000 Independiente fans have arrived in Rio.
In the evening, police said Flamengo fans were chasing Independiente supporters through the streets, especially near the stadium.
Images showed Flamengo fans throwing objects at Independiente's team bus on its arrival at the Maracana. Argentinian fans also had their buses attacked by locals, who threw rocks.
Stun grenades were used in neighboring streets to protect Argentine fans.
The governing body of South American soccer, CONMEBOL, condemned the violence in a statement.
Independiente said CONMEBOL should punish Flamengo.
"This behavior affects the match and, more importantly, the competition. Not only our institution and our fans, but also CONMEBOL's and South American football's image," Independiente said in a statement.
Flamengo chairman Eduardo Bandeira de Mello said he was having dinner with Independiente directors when the fireworks started going off Tuesday night. He said he apologized and asked police to help.
Police also voiced concerns that 300 Argentine fans might mix with Flamengo supporters later, because of tickets offered by the South American soccer body. Touts have also sold tickets to Independiente fans in parts of the Maracana that are set aside for Flamengo supporters.