"We always knew that it was going to be more than one movie -- we knew that from the start -- so we set a trilogy as a sort of placeholder, because we knew there would be more than one movie," Rowling said at the Empire Theatre here on Thursday, reported variety.com.

"But I've now done the plotting properly, so we're pretty sure it's going to be five movies," she added.

Rowling wrote the screenplay for "Fantastic Beasts", which marks her first script.

"So I learned how to write a screenplay while writing a screenplay. I wouldn't recommend it," she said.

During the event, Rowling was joined by Eddie Redmayne, Katherine Waterston, Alison Sudol and Dan Fogler, director David Yates, and producer David Heyman.

The global event was streamed via satellite to gatherings in New York, London, Mexico City, Sao Paulo, and Rome.

Redmayne stars as Newt Scamander in the films.