Vietnam has marked the 50th anniversary of a US massacre of hundreds of Vietnamese civilians during the 1968 Vietnam War.

Hundreds of men and women made it to the My Lai Massacre memorial in Vietnam’s Quang Ngai Province on Friday, a day before the event.

The commemoration comes one week after a visit by a US aircraft carrier to the port city of Da Nang, the first since the war. Bilateral relations have developed between the US and Vietnam since the normalization of their relations in 1995.

On March 16, 1968, American soldiers killed more than 500 unarmed civilians in the area of Son My, marking Washington’s worst war crime registered in the Vietnam War.

My Lai was a typical case of “cruel crimes committed by aggressive and hostile forces” during the war, said provincial official Dang Ngoc Dung, speaking at the Friday commemoration.

A delegation of US Vietnam War veterans and anti-war activists privately met Dung and other Vietnamese officials in a small function room after the ceremony.

The veterans and activists said they were preparing to send a letter, on behalf of the United States, apologizing for the massacre.

“In just a short time, more than 600 people have signed it,” said Chuck Searcy, Vice President of Veterans for Peace.

But the letter apparently does not have the White House’s blessing.