President Dilma Rousseff, a former leftist guerrilla jailed and tortured during Brazil's 1964-1985 military dictatorship, on Wednesday swore in the seven-member panel tasked with probing human rights abuses from that period.

"Brazil deserves the truth, the new generations deserve the truth and above all, those who lost friends and relatives and who continue to suffer as if they were dying again each day deserve the truth," she said, choking back tears as she mentioned names of relatives of the victims.

Also attending the solemn ceremony at the presidential palace were all of Rousseff's living predecessors: Luiz Inacio Lula da Silva (2003-2010); Fernando Henrique Cardoso (1995-2002); Fernando Collor de Mello (1990-92); and Jose Sarney (1985-90), who also is the current Senate speaker.

Over the next two years, the truth panel will probe politically-motivated abductions, rights abuses and murders perpetrated from 1946 to 1988, a time time span even exceeding the dictatorship.

But a 1979 amnesty law for those who carried out the dictatorship-era crimes was upheld by the Brazilian Supreme Court in 2010 and remains in effect.

In a message read aloud during the ceremony, UN High Commissioner for Human Rights Navi Pillay described the creation of the panel as "a necessary and very hopeful step."

"Truth panels are part of a strategy of transitional justice. They can include trials and reparations," the statement added.

This marks the first time Brazil endeavors to provide some accounting for the dictatorship-era rights abuses.

Unlike other South American countries ruled by right-wing dictatorships that committed political abuses and killings from the 1960s to the 1980s -- Argentina, Paraguay, Uruguay and Chile -- Brazil has never put the perpetrators on trial.

The government officially recognizes 400 dead and missing during the military dictatorship, compared with 30,000 in Argentina and more than 3,200 in Chile.

Last year, the Inter-American Court of Human Rights dismissed Brazil's amnesty law as legally invalid, saying it was incompatible with the American Convention on Human Rights.