Ukrainian President Viktor Yushchenko, whose father was detained at Flossenbuerg from December 1944 to April 1945, took part in the memorial service.
"For me this concentration camp has a very human dimension," Yushchenko said, adding that he had a 1944 aerial view of Flossenbuerg showing the camp and the prisoners and that "I know one of those people is my father."
An estimated 30,000 prisoners lost their lives at Flossenbuerg in the southern German state of Bavaria. Many of them were from the Soviet Union and Eastern Europe, including Jews from Hungary and Poland, as well as political prisoners from Germany.
From its founding in 1938 to its liberation on April 23, 1945, by American troops, more than 100,000 people were detained at the camp and its more than 90 external branches.
"I bow my head in front of you," Bavarian Governor Edmund Stoiber said in a speech to the 84 former prisoners who participated in the ceremony. "We will do everything to make sure that you will never be forgotten."
After World War II, parts of the camp were torn down and replaced by a factory and private homes. Only in the mid-1990s did former prisoners start returning to Flossenbuerg to push for a memorial.
Several camp barracks were restored and a research center was opened. The new permanent exhibition will focus on the suffering of individuals.