At least 12 people, including two policemen, were killed during shootouts between rival drug gangs in Rio de Janeiro on the weekend, officials said.
Police said the gangs are battling for control of drug trafficking in the northern sector of the Brazilian coastal city recently chosen to host the 2016 Olympic Games.
Gunfire also downed one police helicopter, causing the death of two officers, the report by the web portal G1 said.
Armed men also destroyed at least five city buses and two schoolrooms in different neighbourhoods of the zone.
Authorities speculated that the attacks on police and civilian targets were meant to distract attention from ongoing gang warfare between various rival factions for control of the hill zone known as "Morro dos Macacos".
Rio will also be one of the country's 12 cities hosting the football World Cup in 2014, including the final match.