Some opposition MPs said the new civil defence concept, to go before ministers on Wednesday, was scaremongering. Citizens are advised to store enough food to last them 10 days, because initially a disaster might put national emergency services beyond reach.
Five days' water - two litres (half a gallon) per person daily - is advised.
The German news website Frankfurter Allgemeine (FAZ) said the new concept was set out in a 69-page German Interior Ministry document.
The document said "an attack on German territory, requiring conventional defence of the nation, is unlikely". But, it said, a major security threat to the nation in future could not be ruled out, so civil defence measures were necessary.
Soon, Germans began tweeting ironically under the hashtag "Hamsterkaeufe" (panic-buying).