MEXICO CITY - Mexican President Andres Manuel Lopez Obrador denied Wednesday that he was a member of the communist party in the 1970s, as alleged in intelligence files that his own government recently ordered declassified.

Lopez Obrador, 65, became Mexico's first leftist president in recent memory after winning election in a landslide last year, along with strong majorities in both houses of Congress for his upstart party, Morena.

The intelligence service's files on "AMLO," as he is widely known, include documents indicating that the one-time protest leader was associated with the communist party in the 1970s, when he was just getting into politics.

"A lot of things in (the intelligence files) are invented. For example, it says I was a member of the communist party... and that I supported and gave money to that party," Lopez Obrador told a news conference.

"I wasn't a member of the communist party -- although I did support social activists."

In the context of Cold War-era Latin America, being a "communist" was practically a dirty word -- and could even amount to a death sentence -- as a slew of US-backed dictatorships used brutal tactics to keep the Soviet-linked ideology at bay in a region the United States considered its back yard.

At the time, Lopez Obrador was a member of Mexico's then-ruling Institutional Revolutionary Party (PRI), which governed as a one-party state for seven decades.

He later broke with the PRI to help launch the left-wing Party of the Democratic Revolution (PRD), then founded his own party, Morena, in 2014.

Lopez Obrador threw open the intelligence service's archives this week, allowing anyone to consult anything in them, except for sensitive details such as information on minors or individuals' private lives.

He vowed to shed light on the intelligence service's involvement in crimes and atrocities committed during the so-called "Dirty War" on leftist activists in Mexico from the 1960s to 1980s.

"There were major injustices committed in the labeling of social activists. A lot of people were repressed. Farmers who didn't even know what communism was were accused and repressed in those years," Lopez Obrador said.

"We must never again allow an authoritarian regime to persecute people for their ideals."

Lopez Obrador's files also indicate he was branded a "traitor" of the left by a member of the now-extinct Unified Socialist Party of Mexico for allegedly sowing divisions in his native Tabasco state to benefit the ruling PRI.

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© Agence France-Presse