Facebook has said it will delete videos of people being decapitated which had been spread on its site.
"We will remove instances of these videos that are reported to us while we evaluate our policy and approach to this type of content," it said.
The news came less than two hours after the BBC revealed a member of Facebook's own safety advisory board had criticised its stance.
The social network had previously refused to ban the clips.
It had said people had a right to depict the "world in which we live".
But the US's Family Online Safety Institute (Fosi) said the violent nature of the material had "crossed a line".
"Personally and professionally I feel that Facebook has got this call wrong," said Stephen Balkam, the organisation's chief executive, ahead of the U-turn.
Charities in the UK had also called on the social network to reconsider its stance saying the material could cause long-term psychological damage.
The warnings came after a one-minute long video was uploaded to the site last week showing a woman being beheaded by a masked man.
A voice heard on the footage suggests that it was filmed in Mexico.
A second video clip showing the execution of two men has also been shared on the network after being posted last Wednesday. The victims say they are drug smugglers for a Mexican cartel before being attacked with a chainsaw and knife.
Ryan L, a university student from Belfast, contacted the BBC after one of the clips spread around his friends' news feeds.
He said he had flagged the material with Facebook as being inappropriate, but was sent the following reply.
"Thanks for your report. We reviewed the video you reported, but found it doesn't violate Facebook's Community Standard on graphic violence, which includes depicting harm to someone or something, threats to the public's safety, or theft and vandalism."
Facebook initially confirmed it had opted to leave such material online.
In reference to the video showing the woman's murder, it issued the following statement:
"People are sharing this video on Facebook to condemn it. Just as TV news programmes often show upsetting images of atrocities, people can share upsetting videos on Facebook to raise awareness of actions or causes.
"While this video is shocking, our approach is designed to preserve people's rights to describe, depict and comment on the world in which we live."
For the past three years Facebook has consulted Fosi and four other organisations in North America and Europe to discuss its online safety policies.
Although the group was not scheduled to meet until September, Fosi's head said he planned to raise the issue during an "extraordinary" phone conference.
"Where it gets grey is: what is in the public interest? Is it in the public interest to know what is going on with the drug lords in Mexico?" asked Mr Balkam.
"But given that not only are teenagers accessing this, but consumer reports estimate that seven and a half million under-13s in the US are on Facebook, you've just got to consider: would this go out on daytime television news?
"I don't think it would, even with a warning saying this is something you may want to avoid. It crosses a line."
He added that one of the videos had been shared among his daughter's schoolmates via Facebook earlier this week.
UK child safety campaigners had also condemned Facebook's policy.
"Facebook must have taken leave of their senses," said John Carr, who sits on the executive board of the UK government's Council on Child Internet Safety.
"I hate to think how an unsuspecting youngster might react if they saw it through their news feed or in any other way."
Decapitation videos can be accessed through sites found via search engines and other popular video clip sites.
However, Dr Arthur Cassidy - a former psychologist who runs a branch of the suicide prevention charity Yellow Ribbon - said Facebook's social nature made it particularly problematic.
He added that he had seen the videos in question and warned they could cause long-lasting psychological damage.
"We know from evidence that [watching] such material can influence self-esteem in a very negative way," he said.
"It can also cause flashbacks, nightmares and sleep disturbance. If that is prolonged it can transfer into many other negative effects in a child and adults as well such as anxiety-related disorders and panic attacks.
"The other problem is some people, in their innocence, might share this with friends to say how abhorrent it is, and we are concerned about the profound and uncontrollable impact this can have on an entire community."
An online petition calling for Facebook to remove decapitation videos had attracted 289 "likes" at time of writing.
One person who supported the campaign wrote: "The video appeared twice on my news feed. I cannot imagine the impact it will have on a younger person. Facebook needs to create some kind of filter to block these images from appearing in the news feed."
Facebook confirmed that its current privacy tools allowed users to block posts by particular people, but not specific types of content.
Mr Balkam said that finding a way to block the spread of such clips to those who had not opted into receiving them was one idea that could be explored.
"If they are going to host this kind of graphic violence how then can we best prevent those videos getting into the hands of folks who really don't want to see these, including children?" he asked.