Beijing police have arrested 11 suspects allegedly involved in a major online provider of high-definition film downloads, whose scale of piracy was described by authorities as "unprecedented".

Illegally run under a Beijing-based technology company allegedly set up by the main suspect named Zhou, silu.com reportedly boasted more than 400,000 registered members and offered unlicensed downloads of 18,772 films and TV series that ranged from arthouse world cinema to domestic and foreign blockbusters, according to a statement released on Tuesday by the National Anti-Pornography and Anti-Illegal Publications Office.

The website, which also provided 3,316 music albums and 208 game software packages, registered 20 million downloads and attracted tens of thousands of visitors daily, the office said.

Uploaders of download sources on the website are said to be based in eight countries and regions, including the United States and Japan.

According to the office, Zhou's company had seven employees, 140 website administrators, two online shops and two brick-and-mortar stores.

The statement revealed that a deeper investigation into the case is underway, and criminal liability will be pursued for profit-oriented uploaders whose offers resulted in more than 50,000 downloads.

According to the statement, suspects in the case also practiced other online business operations such as advertisement sales, hardware sales, user donations and a member credit system.

"The illegal website is suspected of piracy, spreading materials with lewd content and illegal business operations, and the scale of its piracy and dissemination is unprecedented," the statement said.

The action is China's latest effort to strengthen intellectual property rights protection, following the destruction of some 29.44 million pirated publications, including audio and visual products and books, earlier this year.

In another development, a revised draft of the Copyright Law was submitted to the Legislative Affairs Office of the State Council for approval last month.