Coordinated overnight attacks on police by a notorious gang have killed at least 30 people — including 23 officers — in the bloodiest assault of its kind in the history of Brazil's largest state, authorities said Saturday.

Related uprisings at 18 prisons across Sao Paulo state continued Saturday, after scores of armed assaults on police stations, patrol cars and bars frequented by off-duty officers.

The attacks that ended at dawn on Saturday "were obviously the work of the PCC," said Enio Lucciola, press spokesman for the Sao Paulo State Public Safety Department, using the Portuguese initials of the organized crime group First Capital Command.

"It is trying to undermine our authority and intimidate us and the population at large at a time when we have redoubled our efforts to destroy the organization," he said by telephone.

Public Safety Secretary Saulo de Castro Abreu told a news conference that the PCC carried out 55 separate attacks that killed at least 23 police officers, the girlfriend of one of them, a passer-by and five suspected gang members.

The attacks and ensuing gun battles left wounded another 32 people — 15 policemen, 15 attackers and two bystanders — he said.

At least 16 suspects were arrested.

Police set up checkpoints in the low-income Sapopemba district of Sao Paulo, stopping and searching vehicles for weapons. Brazilian TV stations broadcast images of bullet-riddled police cars and shattered glass at a police station that was attacked.

Abreu said police were targeted in Sao Paulo and in the suburbs of Osasco, Guarulhos and Carapicuiba.

Police stations in the coastal cities of Cubatao and Guaruja — about 80 kilometers (50 miles) southeast of Sao Paulo — also were attacked.

Abreu said the attacks were partly reprisal for the transfer and placement in solitary confinement of several imprisoned PCC leaders, a practice authorities use to sever prisoners' ties to gang members outside prison.

Nagashi Furukawa, the Sao Paulo State prison affairs secretary said that the PCC also apparently orchestrated rebellions in 24 of the state's 144 prisons. "Most of these uprisings are minor, and none of the facilities have been destroyed," he said.

Hours later, Furukawa's press office said in a statement that six uprisings had ended and that inmates in the other 18 prisons were holding some 96 hostages. Further details on the uprisings were not immediately available.

"As far as we can tell none of the hostages has been hurt or seriously threatened, which is why we are considering these uprisings as minor," said Marcelo Daniel, a spokesman for the Prison Affairs Department

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 November 2003, the gang 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.