The death toll from the massacre at a bar in Sao Paulo, Brazil's largest city, has risen to seven, with the evidence pointing to the possible role of police officers in the crime, officials said.

The massacre occurred early Saturday at the bar in Campo Limpo, a neighborhood in the densely populated south side of the city, where at least 15 heavily armed men arrived and opened fire at nine people sitting at a table, killing six of them instantly.

One of the wounded died later at a hospital, while two others are still being treated.

The gunmen drove up in three vehicles, shouted "police!" and went to the table at which Paulo Batista do Nascimento, who shot a video two months ago of police killing a man on the same street as the bar is located, was sitting with some friends, officials said, citing eyewitness accounts.

Do Nascimento turned his video over to investigators and five police officers involved in the murder were arrested a few days later.

Eyewitness statements point to the possible involvement of police officers in the massacre, police spokesmen told Brazilian media.

Initial reports said the slayings may have been the work of the First Capital Command, or PCC, the region's dominant criminal organization.

The PCC has been blamed for the surge of violence in Sao Paulo that began in mid-2012.

The attacks attributed to the PCC began in May and, according to official figures, have resulted in the deaths of some 100 police officers - many killed while off-duty - in Sao Paulo and neighboring cities.

The PCC, which controls drug and weapons trafficking in the slums of Sao Paulo and other cities, carried out a series of attacks in Brazil's largest city in 2006.

PCC leaders reportedly run the criminal organization from the prisons of Sao Paulo state, and the gang has become one of Brazil's largest crime groups.

The PCC, also known as the "crime party," first attracted attention in February 2001 when it launched coordinated uprisings in 29 Sao Paulo prisons that left 30 dead and went on for three days.

The current wave of violence was launched by the PCC in retaliation for operations staged by police and death squads against criminals, analysts say. EFE