The feature is being run in collaboration with Samaritans, which said several people had used it during a test phase.
Anyone worried about a friend can fill out a form, detailing their concerns, which is passed to the site's moderators. It follows reports of several cases where Facebook users announced their intention to commit suicide online.
The reporting page asks for the address (URL) of the Facebook page where the messages are posted, the full name of the user and details of any networks they are members of.
Suicide-related alerts will be escalated to the highest level, for attention by Facebook's user operations team.
"When a report is made, they then assess whether they need to call the police immediately or forward it on to us," the BBC quoted Samaritans' Nicola Peckett, as saying.
For the last three months, the system had been operating in a trial mode without publicity, during which it received several genuine reports and no hoaxes, said Samaritans.