By Steve Kingstone
BBC correspondent in Sao Paulo
A United Nations human rights envoy has completed a visit to Brazil concluding that elements within the country's police force continue to kill civilians with impunity.
During her three weeks in the country, Asma Jahangir heard evidence of murder and acts of torture, allegedly carried out by the police and others in authority.
She also met the country's president, Luis Inacio Lula da Silva, who promised to act on the United Nations recommendations.
Off-duty police officers are blamed for many killings
Asma Jahangir was twice moved to tears during this visit by Brazilian women who told how they had watched as their children were shot dead by the police.
She was told of torture in Brazil's jails, of summary executions and of children being abducted by death squads - sometimes linked to the police.
At a final news conference in Brasilia, Miss Jahangir said elements within Brazil's police force displayed a vicious venom in their dealings with the country's poorest citizens.
She said some officers continued to kill with impunity.
Earlier, the UN envoy spoke to Lula. She expressed concern that at present criminal allegations against police officers are investigated locally, rarely resulting in a conviction.
Miss Jahangir urged the government to change the law so that future allegations might be followed up by the federal police.
The government says that reform is already being discussed and that other recommendations will be considered when the UN publishes its final report.
But speaking to reporters the country's justice minister acknowledged that Brazil had a history of generating crime rather than fighting it.
Above all, one event puts this visit firmly into context. In the north-east of Brazil Asma Jahangir heard allegations about a notorious death squad accused of having links with the police.
Among those who came forward with evidence was 24-year-old Flavio da Silva. Just days after meeting the UN envoy Mr da Silva was murdered.