Brasília (AFP) - Tightly-organized groups of protesters planned to bring chaos to Rio's streets during the World Cup final with "guerrilla actions" including the use of home-made bombs, Globo reported on Monday.
The news organization said police thwarted the planned violence through a surveillance operation that began last September and included interception of email and phone calls.
Police last week arrested 23 of the alleged ringleaders of World Cup-related violence.
Citing a police report, Globo said protesters planned to use homemade explosive devices including Molotov cocktails during the tournament's final match, which saw Germany defeat Argentina at the Maracana stadium.
The alleged main ringleader, police say, was Eliza Quadros Pinto Sanzi, known as Sininho, who was among those arrested last week.
According to the police report, the anti-World Cup activists hid their explosives in the city ahead of protests to avoid police detecting them.
Several former protesters, dismayed by the urban violence of radical groups known as Black Bloc, told police about the tactic, the police report said.
It said the protesters organized themselves on three levels, with the first led by Sininho.
Next came an organizing committee that planned the route, procured the explosives and contacted other sympathetic groups.
The third element was the 'frontline' composed mainly of Black Blocs.
Those arrested face charges of participating in acts of violence and association with violent groups.
Supporters of the groups blamed police heavy-handedness at demonstrations that ended in violence.
As it turns out, the anti-World Cup demonstrations were generally far smaller than authorities had feared.
Two of those jailed are accused of the death of a Brazilian TV camerman who was killed when he was struck by a flare during a protest.