LONDON, SEPT. 5 -- Death squads are killing hundreds of street children in Brazil's cities, possibly at the rate of one a day, Amnesty International said in a report for release here Thursday.

Many more children, forced on to the streets to support their families, are being beaten and tortured by police, the London-based human rights group said.

"Poor children in Brazil are treated with contempt by the authorities, risking their lives simply by being on the streets," Amnesty said.

The group said death squads, some of them operated secretly by police, are killing children to "clean up the streets" or remove witnesses to attacks. Brazilian human rights organizations believe that at least one child a day is killed by death squads, Amnesty said.

It quoted the Brazilian Institute for Social and Economic Analysis as saying 457 young people, most with no criminal record, were killed by death squads last year in three cities and that the killings continue.

Amnesty said three boys arrested in Rio de Janeiro in August on suspicion of trying to break into a shop were subjected to Russian roulette. One of the boys, aged 13, was shot in the head and dumped outside a hotel by police. He later died in a hospital.

Police have gunned down youths for failing to obey orders to stop their motorcycles or for alleged insults to officers, Amnesty said. The human rights group said few cases of torture or killing were fully investigated and those that were often took years to go to trial and resulted in light sentences.

Few formal complaints of torture and ill-treatment were made against the police because victims and witnesses were afraid of reprisals, Amnesty said.

It said most torture took place in police custody, although youths in state institutions also were beaten. Amnesty quoted a 14-year-old former inmate of one institution saying, "For any little thing, they like to hit and beat us."