According to witnesses, powerful firecrackers were detonated in the 29th minute of the match and Cerro Porteño supporters took a riot shield from a police officer.
Police responded by firing rubber bullets and tear gas into the stands, forcing hundreds of spectators to flee onto the pitch, television footage showed. The match was suspended and around a hundred people were arrested.
Security forces said at least six police officers were injured, one seriously, and were taken to hospital. It is unclear whether any supporters were injured.
Olimpia leads Paraguay's top division and Cerro Porteño is second.
