Brazil has shone a light into one of the most troubled periods of its recent past, as the government published documents dating from the country's 20 years of dictatorship.

President Luiz Inacio Lula da Silva launched a website on Wednesday containing information dating from 1964 to 1985, when the country was under the sway of the military.

"We are doing Brazilian democracy a service when we unveil some of the mysteries that persist about our past," Lula said at the website's launch.

The portal, which is part of the national archives, includes documents held by state governments and universities.

Dilma Rousseff, the head of Lula's cabinet and the person tipped to succeed him, said the initiative would help end "the culture of state secrets."

But non-governmental groups and families of the victims of the dictatorship called for the government to do more to open the archives of Armed Forces, which they say could cast light on the unknown fate of 140 people who disappeared.

"The website... is a step forward" said Jair Krikchke from the Justice and Human Rights group. "What we are really interested in are the military archives. Brazilians want to know."

Victoria Grabois, of the No More Torture group, said it would also be necessary to open up police files to families of the disappeared. More