Facebook has suffered a series of service disruptions which left many people unable to use the social network.
The problems meant that the site was unreachable for some people for almost two hours.
Sporadic disruptions were reported by many people and even those who could get through said pages were taking a long time to load.
Facebook apologised but said it had fixed the problem.
News of problems getting at and using Facebook spread quickly as people took to Twitter, news sites and blogs to express their frustration.
“Facebook is acting like its stock. It keeps going down,” quipped one Twitter user.
Website watching sites such as Downrightnow and Downforeveryoneorjustme reported that the site was intermittently available for a period of several hours.
There were reports that the hacktivist group Anonymous might have been responsible, but a tweet by YourAnonNews – a widely followed account – noted: “Anonymous would never attack Facebook, we have said this many times. Why would we attack a tool that many anons use to spread info?”
In a statement, Facebook said some users “briefly experienced issues loading the site” but these had been resolved and it should be working fine for everyone.
It gave no details about what had caused the problems.
Facebook has a reputation for reliability and the problems come at a sensitive time for the company. It is under intense scrutiny given the poor performance of its stock following its flotation on the Nasdaq stock exchange 18 May. The stock has fallen almost 23% since its debut.