But Dung said Vietnam wants to set aside the past and befriend other countries to build a better future in which peace and happiness can thrive.
The commemoration comes at a time when bilateral relations between the US and Vietnam are the strongest they've been since their normalisation of relations in 1995. The US is now one of Vietnam's top trading partners and investors, and relations have also expanded to security and defence.
Do Ba was 9 when American soldiers came to his house and rounded up his mother, three siblings and himself and took them to a drainage ditch. His mother and sibling were among the 170 people killed there.
Ba was wounded, covered in blood and buried under bodies. He played dead out of fear the soldiers would come back to kill him. He was finally rescued by a US Army helicopter crew that landed amid the massacre and intervened to stop the killing.
"Twenty years ago, I still harboured hatred against the American soldiers who killed my mother, brothers and sister," he said "But now after 50 years as Vietnam and the United States together developed their relations, people set aside their pain and suffering to build a better society."
At Friday's event, several dozen girls wearing traditional Ao Dai outfits and dove headgear, performed dances in tribute for the victims and to promote peace. Participants including government leaders, villagers and a group of American veterans laid flowers to pay tribute to the victims.
The My Lai Peace Foundation, a local non-governmental organisation, was launched at the event.
"Vietnam had suffered numerous pains of wars," Truong Ngoc Thuy, president of the foundation, said at the launch. "We therefore more than anyone else understand the price of peace, we desire for peace." Historian Duong Trung Quoc noted that as the event was organized a US aircraft carrier was making a friendly visit to a nearby port, the first since the war.
"The war has ended and both nations have learned from its lessons," Quoc said. "The greatest outcome of the lessons is for two nations to come close together in friendship and shared responsibilities, for the benefit of the people in both countries."
Americans who visit My Lai seem as often motivated by guilt as by wishes for a better world. It is a sort of pilgrimage for many and several have established projects, such as school and medical facilities, to contribute to the development of My Lai.
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