FILE PHOTO - The logo of Bytedance's news feed platform Toutiao is seen as its building in Beijing, China October 21, 2017. Picture taken October 21, 2017. REUTERS/Stringer

BEIJING/SHANGHAI (Reuters) - In China, a platform for risqué jokes is no laughing matter.

Toutiao, a hugely popular news and online content portal that is luring investors, was forced to pull its joke sharing “Neihan Duanzi” app, literally meaning “implied jokes”, after a watchdog said it included “vulgar and improper content”.

The move comes amid a broader clamp-down targeting online content from livestreams and blogs to mobile gaming, as the country’s leaders look to tighten their grip over a huge and diverse cultural scene online popular with China’s youth.

China’s State Administration of Radio and Television ordered the app to be taken down permanently in a post on Tuesday for low values that had “caused strong disgust amongst netizens”. It urged Toutiao to regulate similar content on its other sites.

Toutiao, one of the country’s fastest-growing tech start-ups which was valued at around $20 billion last year, has been in hot water with regulators lately. Earlier this week, its main mobile app was also removed from a number of Chinese smartphone app stores following reports of increased censorship.

In a public letter titled “Apology and Introspection”, Toutiao founder Zhang Yiming pledged to raise the number of in-house censors - referred to as content auditors - to 10,000 people from 6,000 currently to keep its content wholesome.

“This product walked the wrong path and had content in deviation of socialist core values,” he wrote in the letter posted on his official microblog account on Wednesday.