Beijing police said Sunday they had detained four people in connection with a sex video taken in a Beijing fitting room that went viral online.

In a press release Sunday night, Beijing police said the four were detained on suspicion of "spreading obscene content".

The document, without naming the four suspects, said one of them was surnamed Sun, a 19-year-old man from northeast China's Heilongjiang Province.

It said Sun was suspected of having posted the sex video at Weibo.com, a major microblogging platform, while the other three were suspected of spreading obscene information.

The video shot on a smartphone shows a young Chinese couple having sex in a fitting room. The offscreen broadcast indicated it was taken in a Uniqlo store in Sanlitun, an upmarket shopping district, in mid April.

Police said the couple admitted having sent the video to some friend at Wechat, a mobile chatting app. But it was somehow hacked and posted on the web, drawing fierce criticism from web users.

Police said they were still investigating the couple, who would face punishment if found to have deliberately spread the footage.

China's criminal law stipulates that those disseminating obscene books, films, pictures and video clips could face up to two years' imprisonment, while those who make obscene products for profit could be sentenced to life.