Twenty-six Chinese audio-based apps are facing punishment ranging from suspended services to app removal over content that spread "historical nihilism" and "pornography," according to a notice published by the Cyberspace Administration of China (CAC) on Friday.

Citing that China’s audio market has been left to "run rampant" for a long time, the statement said some platforms were ignoring regulations and failed to set barriers to prevent teens from accessing restricted content.

Platforms have been using algorithms to work out users' preferences and push content to them, and some even conducted illegal trade across various platforms, it said.

Soul, a voice-based social app whose average number of new daily users reached 162,400 in January, was ordered to suspend its services and is now unavailable in the App Store.

The app, featuring one-on-one chats between strangers and private talk, allows users to communicate anonymously via text or voice messages after being matched by an artificial intelligence algorithm.

Due to the platform's lax control, pornographic and erotic content became easily accessible. 

"Sexual innuendos, images, women moaning are everywhere when you open the app at midnight; it's really gross," said one of the users who had reported the matter to the platform.

"Pornographic voice-based contents spreading ACG (anime, comics and gaming) community culture, audiobooks featuring porn, superstition, zombie, ghost marriages are detrimental to the teenagers' mental development," the notice said, explaining why the CAC has to set "strict regulations on that."

In 2018, online listeners in the country grew 22.1 percent to surpass 400 million, a rate far exceeding that of the mobile video and e-reading populations, according to market researcher iiMedia.

With the rapid development of the "ear economy," the domestic market has gradually been divided by three industry titans: top podcast sharing app Himalaya FM, Lizhi FM and Qingting FM. All three were censored.