Two off-duty police officers were fatally shot, bringing to 73 the number of people killed over the last 10 days in a flare-up of violence in Brazil's largest city, authorities said Thursday.

The officers died in Heliopolis, a sprawling, crime-ridden slum in south Sao Paulo, police said in a statement.

Cpl. Ailton Borges dos Santos and patrolman Antonio Paulo da Rocha were shot shortly before midnight Wednesday as they were riding through Heliopolis on motorcycles.

The men were not wearing their police uniforms.

The shooters took one of the motorcycles as well as the cops' service weapons and official credentials. With their deaths, the number of police officers slain this year in Sao Paulo state climbed to 88.

Six other people were killed in separate incidents Wednesday night in the Sao Paulo metropolitan area.

Police commanders said they don't know why Dos Santos and Da Rocha ventured into a dangerous area at night amid the wave of violence that some civic organizations attribute to a war between law enforcement and organized crime.

That theory has gained credence with the discovery of what appears to be a "hit list" of police officers compiled by the First Capital Command, or PCC, the city's most powerful crime outfit.

Sao Paulo state authorities rejected an offer of help from the Federal Police, Brazilian Justice Minister Jose Eduardo Cardozo told reporters.

The Federal Police contacted the state government to pass on warnings from Brazil's intelligence agencies about the PCC's plans to intensify attacks on law enforcement. EFE