Twenty-three Brazilian police officers have been sentenced to 156 years in jail each for their role in the killing of 111 inmates in 1992 during Brazil's deadliest-ever prison uprising.

The policemen, most of them now retired, were accused of killing 15 prisoners in Sao Paulo's Carandiru prison during the operation to quell the revolt on October 2, 1992, which came to be known as the "Carandiru massacre."

Survivors had described scenes of chaos, accusing police of firing on inmates who had already surrendered or were hiding in their cells. In addition to the 111 prisoners who were killed, another 87 were wounded.

No police were harmed in the operation, but the defence said they fired in self-defence after being threatened and assaulted by the prisoners. Three other policemen in the trial were cleared of wrongdoing.

Defence lawyer Ieda Ribeiro de Souza slammed the narrow verdict, saying she had already appealed against the sentences.

"One vote made the difference. I did not expect any condemnation," she told reporters. "The sentence does not reflect the thinking of Brazilian society. One juror decided the future of these men."

But prosecutor Fernando Pereira da Silva said he was "absolutely satisfied" with the verdict, calling the punishment "adequate."

Fellow prosecutor Marcio Friggi defended the military police as an institution but stressed the need to punish "rotten apples."

Authorities had initially claimed the police were trying to break up a fight between prisoners who had seized control of one of the cell blocks.

But findings later suggested military police had shot prisoners and then destroyed evidence that could have determined individual responsibility for the killings.

No-one is currently serving jail time over the incident.

The commanding officer of the operation, Colonel Ubiratan Guimaraes, was sentenced to 632 years for his mishandling of the revolt and the killings, but in 2006 a court voided the conviction because of mistrial claims.

Later that year, Guimaraes was found dead in his apartment under unclear circumstances.

Another 53 military police officers are to stand trial later for the deaths of the other 96 slain detainees.

"This trial must be a turning point," Atila Roque, Amnesty International's Brazil director, said earlier this week.

"For years, the delay in bringing those responsible for the Carandiru massacre to justice has been a dark cloud hanging over the whole country. We hope that now this impunity is finally coming to an end."

Amnesty said the Sao Paulo state governor at the time and other security officials should also face justice.

The massacre in what was then Latin America's biggest prison, with 8,000 inmates, is seen as a key factor in the emergence of a criminal gang known as First Command of the Capital (PCC) in 1993.

The PCC is believed to have ordered the death of the director of the prison at the time, Jose Ismael Pedrosa.

From the prison, PCC bosses organized a series of assaults on police stations and other buildings that left more than 170 people dead and paralyzed Sao Paulo for four days in May 2006.

The unrest eventually spread to other cities, and scores of suspected criminals were gunned down in a subsequent wave of police reprisal attacks.

Late last year, the PCC was also blamed for a wave of police killings and bus burnings.

The Carandiru prison was demolished in 2002.

AFP