Harry Potter material will be published everyday from December 12 to 23 on the website Pottermore.com as a gift to fans for Christmas, said British author J.K.Rowling.
The author made the announcement on Facebook on Monday, saying the stories will be available each day from 1300 GMT for fans who solve an online riddle.
The new material will include "shiny gold Galleons and even a new potion or two", the author said, and the riddles will be written in rhyme.
The fictional boy wizard has made a few appearances this year in similar publications by the author, but there are no known plans for a new book to follow after the seventh and last volume published in 2007.
Harry Potter has been one of the greatest ever publishing successes, with more than 450 million copies sold around the world and the films raking in $7.0 billion (5.7 billion euros) at the box office.