A notorious criminal gang unleashed a second wave of attacks on police Sunday, bringing to 52 the number of people killed in the deadliest assault of its kind in the history of Brazil's largest state, authorities said.

Another 18 related prison rebellions also broke out Sunday, bringing the number of uprisings across Sao Paulo state to 36. Inmates were holding more than 120 people hostage. The state has a total of 144 prisons.

Officials say the attacks and prison rebellions were planned by the First Capital Command, known by its Portuguese initials PCC.

The attacks were in response to the transfer of several imprisoned PCC leaders, a practice authorities use to sever the inmates' ties to gang members outside prison.

Eight PCC leaders were among 765 inmates transferred to a remote, high-security facility in the far western tip of Sao Paulo state.

The press office of the Sao Paulo state government said the PCC carried out at least 100 separate attacks since Friday that killed at least 35 police officers, the girlfriend of one of them, two passers-by and 14 suspected gang members.

The attacks and ensuing gun battles wounded another 50 people — 36 policemen, eight bystanders and six suspects — the state government's press office said.

At least 16 people have been arrested.

Authorities said police units were on maximum alert, and the federal government said it was ready to help the state with all means available.

Officers in bulletproof vests set up checkpoints to search vehicles, and barriers went up in front of many police stations to keep pedestrians and vehicles away. TV footage showed bullet-riddled police cars and shattered glass at one station.

Assailants also attacked patrol cars, bars where off-duty policemen gather, a courthouse and a highway police outpost on the outskirts of the city of Sao Paulo.

Local media reported the assailants used guns, shotguns, grenades, machine guns and homemade bombs in the attacks in Sao Paulo city, several suburbs, coastal cities such as Santos, Guaruja and Cubatao, and cities more than 185 miles away.

Founded in 1993 by prisoners at the Taubate Penitentiary in Sao Paulo, the PCC is involved in drug and arms trafficking, kidnappings, bank robberies and prison breaks and rebellions, police say.

During a 10-day period in 2003, the PCC attacked more than 50 police stations with machine guns, homemade bombs, shotguns and pistols, killing three officers and injuring 12. Two suspected gang members also were killed.

Those attacks apparently were planned by jailed PCC leaders trying to pressure authorities to improve prison conditions.

In February 2001, the PCC organized a prison uprising that spread to 28 other penitentiaries and jails across Sao Paulo state and resulted in the death of 19 inmates.