Firefighters say at least four people were killed and one wounded at a bar in the city of Belford Roxo in Rio de Janeiro state amid reports that a group of men had opened fire there with guns.
The fire department's press office said that an unknown number of people were taken to hospitals by residents after the Saturday night incident and it did not know their condition, raising fears the death toll could be higher.
Local media, citing police, were reporting that at least four people were killed and seven injured.
Authorities have not provided a motive for the shooting, but much of Brazil's violence is gang related. Rio de Janeiro, the country's second biggest city, experiences daily shootouts between rival gangs and also between police and criminals.