An elite police anti-drugs raid in Rio saw another six deaths

Guaracy Paes Falcao, vice chairman of the Salgueiro samba school, and his wife were killed by unidentified gunmen as he left the group's headquarters.

The deaths coincided with an anti-drug gang raid in Rio by a new elite police force in which another six people died.

Rio's carnival begins on Sunday with a televised traditional parade.

Lottery rings

The shooting of Mr Falcao and his wife happened in Tijuca, a middle-class area surrounded by slums, or "favelas", on the north side of the city.

One unnamed police officer told the Reuters news agency that the shootings could be an "execution", judging by the characteristics of the crime.

A protest in Rio for young crime victim Joao Helio Fernandes

Some samba schools are sponsored by illegal lottery rings, a pairing that has previously led to the death of leading Carnival figures.

Mr Falcao's relation, Waldemir Garcia, an official in Salgueiro, was killed in 2004. Reports say police suspected a link with a turf war over slot machines.

In recent weeks, Rio has seen violent battles between police, drug gangs and self-styled militias made up of off-duty officers who have expelled gangs from about a sixth of the city's slum areas.

The government despatched hundreds of specially trained officers from the national security force in response to violence in December, when gangs set fire to buses and attacked police posts.

In Wednesday's Rio drug raid, more than 100 officers from the elite National Security Force entered the poor neighbourhood of Complexo de Alemao.

Officials say four of the six killed were suspected drug traffickers.

Also on Wednesday about 500 people attended a Mass and then held a protest in Rio in memory of a six-year-old boy, Joao Helio Fernandes, who was dragged to death as thieves stole his mother's car last week.