Facebook announced in May that it would ban videos
showing graphic violence while it carried out a review
Facebook is allowing videos showing people being decapitated to be posted and shared on its site once again.
The social network had placed a temporary ban on the material in May following complaints that the clips could cause long-term psychological damage.
The US firm now believes its users should be free to watch and condemn, but not celebrate, such videos.
One suicide prevention charity criticised the move.
"It only takes seconds of exposure to such graphic material to leave a permanent trace - particularly in a young person's mind," said Dr Arthur Cassidy, a former psychologist who runs a branch of the Yellow Ribbon Program in Northern Ireland.
"The more graphic and colourful the material is, the more psychologically destructive it becomes."
Facebook allows anyone aged 13 and above to be a member.
The BBC was alerted to Facebook's change in policy by a reader who said the firm was refusing to remove a page showing a clip of a masked man killing a woman, which is believed to have been filmed in Mexico.
Some Facebook users complained about a video
showing a decapitation being allowed to remain on the
It was posted last week under the title, Challenge: Anybody can watch this video?
"Remove this video too many young innocent minds out there shouldn't see this!!!" wrote one user in the comments section below.
"This is absolutely horrible, distasteful and needs to be removed... there are too many young minds that can see this. I'm 23 and I'm very disturbed after seeing a couple of seconds of it," wrote another.
The BBC has learned that after reviewing its policies, Facebook decided to let graphic content appear so long it was not celebrated or encouraged by the person who had posted the material.
However, a spokeswoman was unable to provide comment at this time.
Facebook originally pulled such material after the Family Online Safety Institute - a member of its Safety Advisory Board - complained that such videos crossed a line bearing in mind how young some of its members were.
Facebook's terms and conditions now state that it will remove photos or videos that "glorify violence" in addition to other banned material, including a woman's "fully exposed breast".
Decapitation videos are available elsewhere on the net - including on Google's YouTube - but critics have raised concern that Facebook's news feeds and other sharing functions mean it is particularly adept at spreading such material.
Some psychologists have raised concerns that watching
graphic violence can harm the viewer
"I have seen some of these videos - they are profoundly shocking," said John Carr, who sits on the executive board of the UK government's Council on Child Internet Safety.
"Facebook has taken leave of its senses. Those videos will fuel countless nightmares among the young and the sensitive."
The idea of Facebook issuing a blanket ban had, however, concerned some freedom-of-speech campaigners who had suggested it was the responsibility of parents - not the company - to protect children on the internet.
However, the French digital rights group La Quadrature du Net said it was still concerned that Facebook was reserving the right to take down the videos if it took issue with the way they were presented.
"It shows how much Facebook is in power to decide whatever will or will not be expressed through its network," said the organisation's co-founder Jeremie Zimmermann.
"It plays a profoundly anti-democratic role when it makes any such choice, whatever the limits are and whatever the good reasons it uses to make the decision. Only a judicial authority should be able to restrict fundamental freedoms according to the rule of law."