Facebook has said it will not allow horrific self-harm images to be posted on its social media platform as it tightens its policies on content with suicidal practices amid growing criticism of how social media companies limit violent and potentially dangerous content.

Facebook said yesterday that searching for content related to self-harm will now be more difficult for Instagram and will ensure that it does not appear in the recommended materials in the "Explore" section of the photo sharing application.

The Facebook statement on World Suicide Prevention Day follows comments by Twitter that content about self-harm will not be described as offensive in an effort to reduce the stigma surrounding suicide.

About eight million people commit suicide every year, or one every 40 seconds, according to a WHO report.