The blast shattered glass and caused extensive damage to the college in Saarbrucken that has housed the travelling exhibition since last month. No one was hurt.
Police said the assailants had used an electrical detonator, suggesting a level of sophistication not normally associated with neo-Nazi groups. There had been indications recently that the far right was acquiring weapons, but until now well-planned bomb attacks had been thought to be beyond its capabilities.
Since opening nearly four years ago, the display has provoked angry protests in almost every town it has visited. In Munich, neo-Nazis clashed with left-wing counter- demonstrators.
The exhibition, sponsored by the tobacco magnate Jan Philipp Reemstma, purports to show that some members of the regular army were willing participants in war crimes, including the extermination of Jews. Visitors are confronted with diaries of Second World War soldiers, letters sent home from the front, and soldiers' own photographs.
Some of the pictures are especially harrowing. They show Wehrmacht soldiers standing by improvised gallows, or meting out punishment to the civilian populations of occupied eastern Europe.
The exhibition was put together to puncture the convenient official myth that attributes the Holocaust to "Nazis", rather than to Germans. War crimes, according to this view of history, were perpetrated almost exclusively by the Waffen SS and other elite Nazi troops.
Many Germans cling to this version, including the main opposition Christian Democrats, who banned the exhibition from Bonn's History Museum last year.
A spokeswoman for the organisers, the Hamburg Institute for Social Research, said she was shocked and surprised. The attack, she said, showed "how urgently needed such an exhibition is".
A neo-Nazi spattered some of the exhibits with paint two years ago and the organisers had received frequent bomb threats in the past. The display has so far toured 30 towns and cities in Germany and Austria, and has been seen by 700,000 visitors. Before yesterday's attack, there were plans to take it around Europe.Reuse content