A top official during Paraguay's former dictatorship who came home last week must reveal where the bodies of dozens of tortured political prisoners are buried, President Fernando Lugo declared Tuesday.

Lugo, a former Roman Catholic bishop, used biblical terms to demand that Sabino Montanaro reveal the whereabouts of those who died in Paraguay's "Dirty War" against leftists.

"I am going to raise my voice and ask, Montanaro, where are the graves of our brothers?" Lugo said. "To you, who returned to the country and turn to God to wash away your sins, I repeat the question the creator made to Cain when he killed Abel: Where is your brother?"

Montanaro was interior minister under dictator Alfredo Stroessner. Lugo accused him and other officials during Stroessner's 1954-89 reign of hiding the bodies of dozens of slain Paraguayans, saying their unrevealed fate has stymied a healing process and hindered justice since the return of democracy.

"We cannot accept this situation. We cannot tolerate or wait more time without knowing where the graves of the dictatorship's victims are. It's our moral right to uncover this mystery," the president said in a televised statement.

Montanaro arrived in Asuncion early Friday after nearly two decades of self-imposed exile in Honduras. The 86-year-old faces six pending trials for the disappearances and killings of government opponents in the 1970s and 1980s.

Monsignor Mario Melanio Medina, a Catholic bishop who is chairman of the Commission for Truth and Justice, called Montanaro the "cruel right hand of Stroessner."

"The tears and blood of many Paraguayans are weighing on his conscience," said Medina, who was considered a "red bishop" by Stroessner for his alleged communist leanings.

Medina's commission published a report in August saying 59 people are known to have been killed by the dictatorship and 336 more are unaccounted for. It said more than 100,000 were politically persecuted during the dictatorship.

When a military coup toppled Stroessner in 1989, Montanaro sought refuge in the Honduran consulate in Asuncion. Days later he arrived in the Honduran capital, Tegucigalpa, where he lived until returning on his own last week.

While Lugo and human rights activists are seeking answers, the doctor assigned by the government to diagnosis Montanaro's condition said he might not be able to respond.

"We have concluded this individual (Montanaro) is in a confused state, and therefore could not lucidly respond to questions from a judge," forensic doctor Pablo Lemir said at a news conference Tuesday. "He does not locate himself in time or space. He doesn't recognize people."

Attorney Luis Troche, who represents Montanaro, said Monday that his client suffers from a fractured hip, Parkinson's disease, a form of pneumonia and arteriosclerosis. Montanaro is being treated at a police hospital.

Paraguay sought for years to question Stroessner about political opponents who disappeared during the dictatorship, but he died in exile in Brazil in 2006 at age 93 without facing trial.

Human rights groups say the dictatorship was part of a regional network of right-wing military governments that abducted, tortured and killed thousands of suspected leftists.