My Lai massacre photographer laments US 'carnage' fifty years on
Ronald Haeberle (C- with sunglasses) said he came back to My Lai to repent for the horrors of the Vietnam War's deadliest massacre AFP / NHAC NGUYEN

Fifty years after taking photos of an American massacre of Vietnamese villagers, a former US army photographer said he is sorry for the "carnage" his countrymen unleashed in one the war's worst atrocities.

Ronald Haeberle told AFP he started snapping instinctively, capturing the chilling photos that would later expose the full extent of the My Lai massacre: 504 Vietnamese dead in a single day, mostly unarmed women, children and older men.

"I wanted to remember what was happening there, I wanted to capture a moment in time, and I did," he told AFP while touring the My Lai massacre museum in the village on Friday, the 50th anniversary of the killings.

His images, some of which were published in Life magazine in 1969, would eventually help to blow the lid on the cover-up of the massacre, as controversy over the killings cascaded up military ranks and eventually embroiled then-US President Richard Nixon.

The gruesome pictures, some depicting bare-bottomed babies face down in a ditch alongside piles of corpses, added fuel to a mounting anti-war movement in the United States and eventually led to several charges against military officers.

Haeberle was in My Lai, known as Son My by Vietnamese, with US troops on that day in 1968 for what he was told was an ambush to clear Viet Cong rebels from the rice-growing hamlet in central Vietnam, which was believed to be a hotbed of communist resistance.

But as he toured the village with another reporter, he realised most of the dead weren't armed enemies.

"It was complete carnage what we witnessed inside the village, but it happened," he said after a sombre ceremony Friday attended by hundreds of mourners, including massacre survivors, officials and American veterans of the Vietnam War.

"It was a tragedy, something happened that should not have happened. There was no combatants, they were all civilians," he said.

Only one man was ever convicted for the murders -- former lieutenant William Calley -- who said he was following orders from his superiors on the "search and destroy" mission. Calley publicly apologised for the killings in 2009.

Haeberle said he was brushed off by some of those military officers on March 16, 1968, when he pressed them on what happened.

He recalled how a Vietnamese interpreter pleaded with the American army captain in charge of the battalion that carried out the murders.

"He kept saying 'Why are they shooting my people? Why? These are civilians'. He was visibly upset," Haeberle recounted.

Like hundreds of US war veterans who have returned to Vietnam since the war ended in 1975, Haeberle -- who has previously visited My Lai -- came back to Son My to repent for the horrors of the war's deadliest massacre.

"I'm able to pay my condolences to the survivors and the ones that were deceased... hopefully they accept my apology for what happened on March 16," he said.