"We're working to resolve the issue as soon as possible".
"We're working on getting it fixed as soon as we can", a message told many users as they tried to post content.
When some users try to post they are met with an error message.
Additionally, The Verge reports that some users are experiencing similar problems with Mark Zuckerberg's original social network. Both Facebook's desktop site and app appeared to be affected.
One said: "Facebook, Messenger and Instagram are down and here I am ranting on Twitter".
Facebook later confirmed that the issue is not related to a DDoS attack, in which hackers overwhelm the site with fake traffic, reports explain.
This message says Facebook will be back in a few minutes, but the problems have persisted for a longer time.
Facebook makes more than $90 million a day in ad revenue, so any extended outage of its main advertising conduit adds up.
Some Twitter users who work in "Facebook-centric" jobs, expressed their panic and distress at being unable to use the platform.
This is a developing story and will be updated as more information becomes available.