German Foreign Minister Heiko Maas pledged on Sunday to fight Holocaust denial as a trio of former Nazi concentration camps mark the 75th anniversary of their liberation in the shadow of the coronavirus pandemic.

Memorial ceremonies have had to be cancelled or dramatically scaled back for the camps at Sachsenhausen, Ravensbrueck and Bergen-Belsen.

"Over 20,000 people lost their lives in Sachsenhausen concentration camp. If we held a minute of silence for each of them, there would be silence for two weeks," Maas said in a video statement.

"But the fight against forgetting may not be silent," he added.

Germany assumed the chairmanship of the International Holocaust Remembrance Alliance last month, and Maas said it would use the year at the helm to "fight against those who deny or distort the history of the Holocaust."

"When remembrance is vilified as a “cult of guilt” and victims reframed as perpetrators, be this in Germany or abroad, we Germans cannot remain silent," he said.

Sachsenhausen, located just north of Berlin, is one of several former camps which were liberated by Allied forces 75 years ago this week. 

The Sachsenhausen memorial centre, which had planned a number of events from Friday to Tuesday but has closed along with others, moved commemorations online with a series of video clips including Maas' statement. 

Smaller ceremonies were also held on Thursday at Sachsenhausen and nearby Ravensbrueck. 

At Bergen-Belsen in Lower Saxony, memorial centre employees laid flowers at the "Wall of Inscriptions", while Germans across the country observed a minute's silence to mark the liberation anniversary last Wednesday. 

More than 50,000 people died at the Bergen-Belsen camp, including the diarist Anne Frank, whose accounts of the Holocaust have become a symbol of the suffering inflicted by the Nazis during World War II.

Commemorative events originally planned for Sunday have been postponed to April 2021, and some of the planned speeches were also delivered online.

"For us in Lower Saxony, Bergen-Belsen is the place that shows us the cruelty and mercilessness of the darkest part of our history," said regional state premier Stephan Weil.