A Brazilian rightwing group led by a messianic cult leader who claimed to be in contact with aliens carried out terrorist acts to justify repression by the country’s military dictatorship, according to newly discovered archive documents.

The revelation landed days before the country’s presidential election, amid a polarized campaign in which the frontrunner – far-right candidate Jair Bolsonaro – has praised the dictatorship era as a golden age.

According to an investigation by the independent news agency Publica, which drew on archive documents, the paramilitary group carried out terrorist attacks so that military rulers could tighten repression.

Archive documents – including records of group members’ interrogations – revealed that the attacks were secretly encouraged by a general who was close to then president Arthur da Costa e Silva and in contact with federal police.

The revelations added to other reports of state-sponsored, rightwing terrorism attacks during the military regime which ran Brazil from 1964 to 1985.

“There has always been a certain suspicion that groups of the right had actually organised to do some attacks. What is surprising is the richness of detail in these documents,” said Luiz Dias, a professor of history at the Pontifical Catholic University in São Paulo and specialist in Brazil’s dictatorship.

The group was led by Aladino Félix, who wrote a book called My Contact with Flying Saucers under the pseudonym Dino Kraspedon, claimed to be the messiah of the Jewish people and had served in the army during the second world war.

“He was seen as a crazy guy,” said Vasconcelo Quadros, who conducted the investigation, “but he had a relationship with the authorities.”

Félix led a group of 14 police officers who, between December 1967 to August 1968, carried out a series of terrorist acts – detonating 14 bombs, stealing arms and explosives and robbing a bank. Targets included the São Paulo stock exchange, a secret police headquarters and an oil pipeline.

In March 1968, armed leftist groups also began planting bombs. And as violence increased, in December 1968, the military government used leftwing terrorism as its justification to introduce a landmark decree that toughed up the dictatorship’s powers, ushering in its most repressive period, which became known as the anos de chumbo, or years of lead.

A 2014 report by Brazil’s truth commission blamed the dictatorship for 434 killings and disappearances.

Félix and his group were arrested in 1968. Félix served a little over three years in prison, Quadros said, and eventually died in 1985.

In 1981, a sergeant was killed and a captain injured when a bomb in a car they were waiting in at the Rio Centro convention centre in Rio de Janeiro exploded. Both were members of the Doi-Codi intelligence agency, a CIA document published this year revealed.