The wave of violence in Sao Paulo claimed the lives of 13 more people between Sunday night and the early hours of Monday, Brazilian police said.

The latest killings raised the death toll from the weekend's violence to at least 23, with 12 of the murders committed by gunmen traveling on motorcycles or in automobiles.

The wave of violence that started last month in Brazil's largest city has left about 300 people dead, unofficial tallies show.

Officials have not released complete murder figures for the urban violence.

More than 90 police officers, many of them off duty, have been murdered this year in the city.

Officials suspect that the First Capital Command, or PCC, a gang founded in 1997, is behind the attacks and killings.

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 said. EFE