Dozens of popular Chinese writers have accused the search engine giant Baidu of infringing on their copyrights and branded it a "thief" in the latest claims of piracy against the company.

More than 40 writers, including the popular blogger Han Han and well-known writer Jia Pingwa, have signed a letter claiming Baidu provided their works for free download on its online library, Baidu Wenku, without their permission.

"Baidu has become a totally corrupt thieving company," the authors said in the letter posted on Tuesday on the website of the China Written Works Copyright Society.

"It stole our works, our rights, our property and has turned Baidu Wenku into a marketplace of stolen goods," it said.

Baidu Wenku, launched in 2009, allows users to read, share or download files and books, or their excerpts, for free. Readers can also purchase books from the online library - at a much lower cost than the cover price.

All documents are uploaded by Internet users. As of November, Baidu Wenku had stockpiled more than 10 million files and books, accounting for 70 percent of China's online file-sharing market, according to the company's figures.

Baidu's spokesman Kaiser Kuo said the search engine "attaches great importance to intellectual property rights protection" and had deleted "tens of thousands of infringing items" uploaded by Web users.

"We promised that authors or copyright holders can report problematic content found on Baidu Library to the complaint center ... and we will delete infringing content within 48 hours," Kuo said in a statement on Wednesday.

In a disclaimer on its website, Baidu said users who uploaded the files must accept all liabilities and be responsible for compensation in any copyright disputes.

However, the writers insisted Baidu should bear responsibility, claiming the company took advantage of the uploads to "enhance its own influence, boost its stock price and increase its profits".

"We do not blame the friends who uploaded (the documents). We only blame the evil platform of Baidu," they said.

Zhang Hongbo, deputy director general of the China Written Works Copyright Society, also said on Tuesday that the society is collecting more evidence and may sue Baidu for copyright violation.

Baidu has long been criticized for flouting intellectual property rights. Its MP3 search service, which provides links to free but sometimes pirated music downloads, has drawn fire from the recording industry.

The Office of the United States Trade Representative last month named Baidu as one of the world's top marketplaces for pirated and counterfeit goods, saying the company was enabling piracy with "deep linking" searches.

Baidu has around 75 percent of the Chinese search market, compared with the 19.6 percent held by Google, which has been losing ground since a public spat with Beijing last year over alleged censorship, according to analysts.