Harry Potter author J.K. Rowling is planning to make a trilogy of spin-off films based on a Hogwarts textbook from the fantasy franchise, according to a movie studio executive.

The writer announced last year (13) that she was set to make her screenwriting debut with Fantastic Beasts and Where to Find Them, the first in a new series, which was described as "neither a prequel nor a sequel to the Harry Potter series, but an extension of the wizarding world".

Now Warner Bros. boss Kevin Tsujihara reveals fans can look forward to three instalments of the project, which follows the adventures of Newt Scamander, a magical creatures expert known as a "magizoologist".

The story is set in New York, 70 years before the Potter series begins.

Production and release dates have yet to be determined.

The Potter books spawned a total of eight movies, starring Daniel Radcliffe as the young wizard, and raked in $7.7 billion worldwide, making it the highest-grossing film series of all time.