"The number of nominations increases almost every year, which shows a growing interest in the prize," the head of the institute, Geir Lundestad, told AFP.
"We receive nominations from absolutely everywhere in the world," he added.
The Nobel committee convened today for the first time this year to examine the candidate list.
All nominations -- which can be made by lawmakers, university rectors and others deemed to have the right qualifications -- had to be sent before the February 1 deadline to be valid.
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The list is kept secret for at least 50 years, and Lundestad revealed only that 47 of the 278 candidates were organisations.
The name of this year's laureate is to be announced on October 10 in Oslo.
Last year saw 259 nominations, then also a record, and the prize was awarded to the Organisation for the Prohibition of Chemical Weapons (OPCW), involved to this day in the dismantling of the Syrian chemical weapons arsenal.