Thousands of websites have been shut down and links to offending sites deleted in a battle against intellectual property infringement, China's copyright watchdog said.

Since a national campaign to protect IP rights began in July, supervisory departments performed 55,000 evaluations of websites, either online or at physical premises, and subsequently closed down 1,655 sites.

Some 274,800 links to the sites were deleted, while law enforcement officers confiscated more than 1.5 million printed books, CDs and DVDs, according to a statement from the National Copyright Administration of China.

Some 314 cases involving alleged online infringements were filed for investigation by the copyright authorities. Of those, 37 were investigated in cooperation with local police.

Provinces and cities released guidelines to tackle IP infringement in media and avoid unauthorized reprinting and reposting of articles, including in Shanghai and Beijing; Henan and Fujian provinces; and the Guangxi Zhuang autonomous region.

Films and television programs were targeted in particular. Officers from Zhenjiang, Jiangsu province, detected a website that had distributed more than 30,000 films. The main suspect had gained more than 8 million yuan ($1.2 million) illegally, the police said. Beijing deleted 20,856 pirated film links on 562 websites.

The battle also targets online apps. An app in Chongqing that illegally spread music works was fined 20,000 yuan.

Online stores were also targeted. A man identified only as Zhao, who sold pirated copies of various works on Taobao, a major e-commerce platform, was sentenced to three years in prison and fined 170,000 yuan, according to the statement.

The annual campaign, called Internet Sword, began in 2005 and aims to tackle online copyright infringement. It targets music, movies, literature, games, e-commerce and software. It is expected to last until the end of December.

"To protect the copyrights of movies, TV series and news stories online, the effort will severely strike websites and other platforms, such as cloud storage and social media platforms, that spread unauthorized works," said Yu Cike, director of copyright management for the National Copyright Administration, at the start of the 2017 campaign.

"It will also target websites, mobile apps and WeChat accounts that publish, repost or spread news articles without authorization," he said.