Some of China's biggest video streaming sites have been warned that they face punishment after failing to remove explicit Japanese cartoon video clips.
China's Ministry of Culture said the firms had hosted anime that glorified violence and terrorism, and contained "vulgar" erotic elements.
Net firms Baidu, Tencent and Youku were among those named as offenders.
The announcement coincides with the introduction of wider restrictions on the use of foreign online clips.
Streaming sites now require publication licences to be able to add other countries' TV series and movies, which will be judged by the State Administration of Press, Publication, Radio, Film and Television (SAPPRFT) on an individual basis. Unregistered clips must also be removed.
The official news agency Xinhua has noted that local TV stations rarely screen imported series because they are supposed to favour domestic productions.
Three specific examples of indecent anime cartoons are mentioned in a statement posted to the Ministry of Culture's website:
- Blood-C, a series about a sword-wielding teenage girl who fights monsters in her town. It is accused of containing a "particularly bloody" beheading scene that would cause "extreme discomfort"
- Terror in Resonance, a series involving two teenagers who carry out a terrorist attack with a nuclear weapon. Officials said this glorified violence and criminal activities
- High School of the Dead, a show about a group of students struggling to survive in a world overtaken by zombies. The programme, which was given a certificate 15 when released in the UK, is accused of being borderline-pornographic
The ministry noted that 12 offending clips on Todou alone had attracted more than one million hits.
The firms involved have been told they will learn what penalties they face at a later stage.
Officials also announced plans to issue a "blacklist" of banned content to help the firms meet their obligations.
The move was attacked by an editorial published on Shenzhen-based news site Qianzhan.com, which questioned why adult-themed content could not be restricted to the over-18s, as is the case in Hong Kong and Taiwan.
Beijing is engaged in wider efforts to restrict what foreign online content its citizens can access, via the use of a system known as the Great Firewall of China.
But one expert suggested the fact anime had been singled out for criticism, might feed into specific concerns about the spread of that genre.
"The sexualisation of child-like women may be a legitimate concern to the Chinese government," said Professor Leslie Young from the Cheung Kong Graduate School of Business.
Another academic, however, said it signalled that the government was becoming more restrictive.
"Most websites and publications have a pretty good idea of what they can get away with," said Prof Karl Gerth, who holds a chair in Chinese studies at the University California, San Diego.
"And, for the past few years, they have internalised the more restrictive preferences of the new Xi Jinping regime.
"For this to break out in the open suggests the leeway to publish online or in print 'controversial' material of all sorts continues to narrow."