Facebook and Instagram have suffered a global outage.
Thousands of users have reported being unable to access the social media sites in Ireland, and across Europe, the United States, South America and the Far East.
Website Downdetector, which tracks technology failures online, indicated tens of thousands of problems were reported on both sites between 3pm and 6pm.
Almost 90% of problems on Facebook were reported as total blackouts or users being unable to log in, while on Instagram the core issue was with its news feed.
Facebook, which also owns Instagram, wrote on its developer site: "We are currently experiencing an increased level of API errors. We are investigating the cause, and we'll post updates when we have more information."
Many users used other social media outlets to vent their frustration, with the hashtag #FacebookDown trending on Twitter.
The Facebook people wondering into Twitter like#facebookdown pic.twitter.com/e80oAvKA8C
— KelevRa (@spyke181) October 11, 2017
With #facebookdown please note that posting photos of your dinner, the cake you just made or your shiny nails are against #twitter rules
— friday_the_12th (@friday_the_12th) October 11, 2017
#facebookdown that awkward moment when you find out that Facebook is down, on Twitter ....................
— Leigh, Ghost seal enthusiast, #Orca 2024 (@freckle_red) October 11, 2017
As #facebookisdown, had a good face to face conversation with a couple living with me, just found out they are my parents#facebookdown
— The Lol Buddhu (@lolbuddhu) October 11, 2017
Facebook and Instagram are down... and have been for the last hour. Nobody panic! #facebookdown pic.twitter.com/SZP3vxCiJs
— All Tee All Shade (@AllTee_AllShade) October 11, 2017