A number of noted publishers and copyright owners held a press conference in Beijing last week to protest a promotion campaign by China's largest online bookseller Dangdang.com more than two months ago.

As part of World Book Day, Dangdang organized a "zero yuan promotion" from April 17 to 19, when all copyrighted digital books on the portal could be downloaded for free.

Publishers delayed their reaction because Dangdang is an important distribution channel for their paperback books, said Bi Yu, vice general manager of ZZHW Digital Media Co, a subsidiary of China Writers Publishing House.