Two people burned to death over the weekend when a bus was torched in Sao Paulo, which has been plagued by a wave of violence blamed on a gang that operates inside the prisons, Brazilian police said.

About 20 people attacked the bus early Sunday at a terminal in the northern section of the city, eyewitnesses said.

The only two passengers aboard the bus were trapped and burned to death, police said.

Seven suspects were arrested in connection with the attack on the bus, police spokesman Cosmo Stikovics Filho said.

Sao Paulo, Brazil's largest city and main financial center, has experienced a spike in urban violence since May.

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

Nearly 100 police officers have been murdered in Sao Paulo and neighboring cities since May, with the majority of the officers being killed near their homes while off duty.

A total of 180 people, according to official figures, were murdered in Sao Paulo in October, a figure that was up 114 percent from the same month in 2011.

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