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.