People in Argentina have taken to the streets to protest President Barack Obama’s visit, coinciding with the 40th anniversary of a US - backed military coup that led to seven years of a bloody dictatorship. Demonstrators, including human rights groups and leftists, marched in the capital Buenos Aires on Wednesday, expressing their anger at Washington’s support for the 1976 coup. “It’s a march against Obama’s visit; also against the Argentine government, who received him with honors,” said Alejandro Bodart, director of the Workers Socialist Movement. “The left are mobilizing against Obama because it is a slap in the face that on the 40th anniversary of the coup the head of North American imperialism, which supported the coup at the time, arrives,” he added. The US initially backed the military dictatorship that ruled Argentina from 1976 to 1983. Some 30,000 people were killed in a bloody crackdown against leftist opponents and labor unions. Many were “forcibly disappeared” and hundreds of children were stolen from their detained mothers. Obama reiterated a pledge Wednesday to declassify US military and intelligence documents about Washington’s role in the military dictatorship. “I hope this gesture helps rebuild trust that may have been lost between our two countries,” the president said. Activists, however, believe the documents will be highly redacted before being declassified. “I don’t believe there will be anything in those documents – they always black out the names and the important parts,” said Nora Cortiñas of the Mothers of Plaza de Mayo. Obama and Argentine President Mauricio Macri were to attend a ceremony to commemorate the victims of the dictatorship on Thursday. The planned visit to the memorial promoted anger among the rights groups, who believe Obama’s presence will encroach on painful memories for many people who still continue to search for missing victims. “It’s a provocation, it’s our date,” Cortiñas said. Marches have been organized in Buenos Aires and across the country for Thursday afternoon. “More people and especially more young people are turning out to march every year,” said another activist from Mother of Plaza de Mayo.