BERLIN (AP) — A ceremony has been held at the former site of Germany's Buchenwald concentration camp to remember people imprisoned there because they were thought to be gay.

The commemoration on Sunday was part of events in the nearby town of Weimar for Christopher Street Day, Germany's LGBT pride observance.

About 50 people marched through the grounds of the Buchenwald Memorial holding a rainbow flag and placed flowers at a marker for 650 camp prisoners who were assigned uniforms with pink triangles between 1937 and 1945.

Nazi Germany forced people to wear pink triangles to identify them as gay. Many of the prisoners lost their lives at Buchenwald, but how many is unknown.

Weimar's Christopher Street Day group said it wanted to "commemorate the prisoners who had to suffer because as men they loved men."