The shortfall, expected to last into January, amounts to between 500 and 1,000 tonnes, said Tine, Norway's main dairy company, while online sellers have offered 500-gramme packs for up to 350 euros ($465).

The dire shortage poses a serious challenge for Norwegians who are trying to finish their traditional Christmas baking -- a task which usually requires them to make at least seven different kinds of biscuits.

The shortfall has been blamed on a rainy summer that cut into feed production and therefore dairy output, but also the ballooning popularity of a low-carbohydrate, fat-rich diet that has sent demand for butter soaring.