Twitter has apologised after pornographic footage was promoted as an "editor's pick'' on its new Vine video app.
The six-second video with "adult content" was promoted less than a week after the service launched.
Twitter blamed human error and said the video has been removed.
A spokesman said: "A human error resulted in a video with adult content becoming one of the videos in Editor's Picks, and upon realising this mistake we removed the video immediately.
"We apologise to our users for the error."
Photographs circulated on the social network showed a video posted by a user called NSFWVine - seemingly a reference to the "not safe for work'' warning some Twitter users use when posting risque content.
With "editor's pick'' in the corner, the cover screen said: "Warning. This post may contain sensitive content. Tap to view."
Vine, which was launched last Thursday, is an app that lets users of the social network post very short films from their mobile phones.
Dick Costolo, Twitter's chief executive, posted footage using the software through his @DickC account, showing him making steak tartare in a video that resembled gif animated footage.
Twitter's vice-president of product Michael Sippey wrote on his blog: "Like tweets, the brevity of videos on Vine (six seconds or less) inspires creativity.''