Survivors of the Buchenwald and Mittenbau-Dora concentration camps will gather at a wreath-laying ceremony Monday to mark the moment the sites were liberated from Nazi forces, exactly 77 years ago.

Buchenwald was the largest concentration camp within Germany's pre-war 1937 borders; hundreds of thousands of imprisoned people from all over Europe passed through it during the war. Mittelbau-Dora was its extension.

The annual commemoration of the sites' liberation was  disrupted by COVID-19 in the last two years. But about 500 people, including survivors and their families, attended a Sunday event — part of remembrance commemorations spanning a week — at the Buchenwald camp, near the Central German city of Weimar.

Only 16 survivors from the Buchenwald prison camp are alive, prompting Jewish leaders to call for renewed efforts to remember the horrors of the holocaust when 6 million Jews were killed.

"What people are capable of, we see today not far from us," said Josef Schuster, head of Germany's Central Council of Jews, referring to the war in Ukraine.

Buchenwald prisoners freed

The US army first reached Buchenwald on April 11, 1945, freeing some 21,000 prisoners held there at the time.

Starting from 1937, Nazi forces had captured and sent some 280,000 people to Buchenwald and its 139 sub-camps.

The prisoners were mainly Jewish, but also Roma, Sinti, Poles, homosexuals and others that were systematically targeted for extermination by the Nazis.

At Buchenwald, the prisoners were forced to produce weapons. Many were also used in medical experiments. Some 56,000 people died from executions, diseases and starvation.

Mittelbau-Dora was initially a Buchenwald sub-camp but later operated independently. Around a third of its 60,000 population died before the end of the war.

Ukraine war threatens holocaust survivors

The anniversary comes at a time of renewed upheaval that has seen 10,000 holocaust survivors living in Ukraine threatened by war.

Some who lived through the horrors of the death camps have since fled their country as Russia's assault on Ukraine continues.

Anastasia Guley, 96, who was present in Buchenwald on Sunday, was imprisoned in Buchenwald, Auschwitz and Bergen-Belsen camps.

Guley now lives in the German state of Saxony-Anhalt, close to the Buchenwald site.

Buchenwald survivor Boris Romantschenko who was killed this month after Russian missiles hit his apartment building in the devastated city of Kharkiv, was specially remembered at this year's liberation anniversary.

"I basically regret that I'm still alive because this is now the second time I have to experience a war," said 90-year-old Alla Senelnikova, a retired doctor also from Kharkiv.

Germany barred delegates of Russia from attending this year's Buchenwald ceremonies in light of the war in Ukraine, despite the then-Soviet Union's key role in Hitler's defeat.

sl/msh (dpa, epd)