Rowling said in a message on her website that the since-closed site, www.harrybooks.info, had been offering what it alleged to be an e-book version of "Harry Potter and the Half-Blood Prince", due for release in July.

The offer, she said, was a scam.

"You should NEVER trust any Harry Potter e-books offered for download from the internet or on P2P (Peer-to-Peer)/file-trading networks," Rowling said.

"Setting aside the fact that these books are illegal (there are no authorized HP e-books to date), they may infect your computer with viruses, leave you vulnerable to the dangers of hacking and/or credit card fraud, and may also contain content that has nothing to do with Harry Potter, to say the least," the author warned.