German President Frank-Walter Steinmeier on Thursday asked Greece for forgiveness for crimes committed during the Nazi occupation.
His comments came at the site of the former Haidari concentration camp near Athens.
"Unimaginable atrocities were committed under German auspices in the Haidari camp. We bow before the victims," Steinmeier said at the camp, where up to 25,000 people were interned, according to Deutsche Welle.
During World War II, between 60,000 and 70,000 Jewish Greeks were murdered in mass shootings and other atrocities. Steinmeier said Germany's moral and political responsibility for this must not be forgotten.
Steinmeier's visit, on the anniversary of the liberation of Athens, came after Greek Prime Minister Alexis Tsipras' government renewed Greece's claims that Germany still owes vast sums in war reparations.
Greek officials said last month Athens will seek parliamentary approval this year to further their claims against Germany, which date back to the 1990s.
A 2016 parliamentary report found Germany owed more than €270 billion, including the repayment of a €10 billion "loan" the Bank of Greece was forced to grant the Nazis.
Berlin argues the issue was definitively resolved in a previous, wider post-war agreement.