Brazil's Senate on Wednesday agreed to set up a Truth Commission to investigate human rights violations during the country's 1964-1985 military dictatorship, officials said.

The legislation passed, according to the congressional news agency, having already been approved by the House of Deputies, and now awaits President Dilma Rousseff's signature to take effect.

Rousseff, a former guerrilla fighter now aged 63, is Brazil's first woman and second leftist to be elected president.

She had urged Congress to act swiftly on the Truth Commission bill -- seen as key to national reconciliation -- which was put before lawmakers by her predecessor, also of the Workers Party, Luiz Inacio Lula da Silva.

The commission is meant to investigate issues including politically motivated abductions in the Cold War-era, rights abuses and murders over a time span longer than the dictatorship -- 1946-1988.

It does not however lift an amnesty for those who carried out the repression, in effect since 1979, and upheld last year by the Supreme Court.

Brazil has acknowledged 400 abductions and presumed deaths during the dictatorship.

Other countries in southern South America which had right-wing dictatorships and political abuses and killings during the 1960s-80s -- Argentina, Paraguay, Uruguay and Chile -- have put some of the perpetrators of the era on trial.

Brazil, however, has not.