Baidu, China's biggest online search engine, has deleted 2.8 million unauthorized works of literature, or more than 99 percent of the material in the literature category that had previously been freely available on its Wenku system.

The number of available works had shrunk to 447 by 9pm yesterday, mostly ancient classics or novels uploaded voluntarily.

The move came after a promise Baidu made on Sunday that it would delete all unauthorized literature within three days as an apology for "hurting the feelings" of writers and publishers who had launched an online campaign claiming the free file-sharing platform infringed their copyrights.

Baidu CEO Robin Li said on Monday that he would shut down the Wenku system if it could not be well managed.

The removal of the copies was welcomed by the Anti-Baidu or Anti-Copyright Infringement Alliance in a statement on its Sina microblog.

But Shen Haobo, a poet and publisher of the announcement, said there was still a huge amount of non-literary copyright material in the Wenku system available for free downloading.

In the announcement, the writers said they regarded Baidu's action as a turning point but not the end of the battle over copyright infringement because of doubts about Wenku's new system which was also launched yesterday.

The Cooperation Platform aims to seek the cooperation of writers and publishers by offering a share of advertising fees and sales from paid-for e-book services.

But the writers expressed doubts over whether the new system would protect their works from future copyright infringements.

Meanwhile, a campaign led by musician Gao Xiaosong and several record company CEOs has been launched to target Baidu over the offer of music downloading services.