Following mounting pressure from critics and its own internal safety advisors, Facebook has started placing warnings for graphic videos and images that have been flagged as offensive or inappropriate by other users.

Facebook has confirmed to the BBC that it has started displaying the warnings in December. If users choose to ignore the warning, they can simply click to play the videos. Previously, Facebook has rolled out auto-play for all videos on the News Feed, which could be potentially dangerous if graphic videos automatically start playing without adequate warning to its viewers.

"When people share things on Facebook, we expect that they will share it responsibly, including choosing who will see that content," says a Facebook spokesperson. "We also ask that people warn their audience about what they are about to see if it includes graphic violence."

Facebook also says it is preventing users registered below 18 years old from seeing the videos and images altogether.

"In instances when people report graphic content to us that should include warnings or is not appropriate for people under the age of 18, we may add a warning for adults and prevent young people from viewing the content," the spokesperson says.

Among the first pieces of content to be affected is a video of the shooting of police officer Ahmed Merabet, who was murdered during last week's terrorist attack at the office of the Parisian satirical publication Charlie Hebdo.

Facebook has always had the challenge of maintaining a balance between ensuring freedom of speech and protection of children on the Internet. Whatever it plans to do, the social network will always have some form of criticism from either side, as free-speech activists would call it out for censorship if it decides to ban graphic videos and child protection advocates would slam it for failing to protect children from psychologically damaging content.

In 2013, Facebook started adding warnings over videos depicting beheadings in Mexico after United Kingdom Prime Minister David Cameron called the social network "irresponsible" for allowing the graphic videos to remain on the site. The videos were later banned altogether.

However, Facebook continues to allow violent and graphic content that is deemed to be of public interest or concern, such as videos and images of human rights abuses and acts of terrorism, although it explicitly says that it does not allow "graphic images shared for sadistic effect or to celebrate or glorify violence."

The issue resurfaced once again in August when images of human heads placed on spikes in Syria appeared on the social network, prompting the Family Online Safety Institute (Fosi), a member of Facebook's internal safety advisory board, to demand that Facebook place covers over graphic images and institute a system that prevents minors from seeing them.

Fosi CEO Stephen Balkam says he is "delighted" by Facebook's latest move to prevent users from viewing distressing images without warning and lauded Facebook because "it has walked a fine line between protection of users and protection of free expression and... it has got it just about right."

Still, others, such as psychologist Arthur Cassidy of the Yellow Ribbon suicide prevention program, believe Facebook should institute an overarching ban on all graphic videos and images. Cassidy says many users below 18 years old use Facebook and can easily get around the restrictions to these disturbing videos.

"We know if we say, 'Do not do it,' that they will still do it - they will want to look and view material, irrespective of how grotesque it is," he argues. "And it has the potential to influence maladaptive behavior in those who might have the potential to become aggressors themselves."