Facebook, WhatsApp and Instagram all go down in major outage
The platforms confirmed on Twitter they are aware of issues and are working to resolve them.
According to web service monitoring platform DownDetector, thousands of people reported outages before 5pm on Monday.
Data on its website showed that almost 50,000 people had reported the outages on Facebook.
Most complaints cited issues with the website (72%), while others were linked to issues with the server connection and the app.
Moe than 60,000 had complained about WhatsApp, with 43% reporting issues with the app itself, while 28% cited the server connection and 28% relating to sending messages.
More than 30,000 Instagram users also had similar complaints, with 51% relating to the app, 26% over the server connection and 23% citing the website.
A graph on the DownDetector website showed a clear spike from after 4pm.
Whatsapp said on Twitter: "We're aware that some people are experiencing issues with WhatsApp at the moment.
"We're working to get things back to normal and will send an update here as soon as possible. Thanks for your patience."
Facebook account tweeted: "We're aware that some people are having trouble accessing our apps and products.
"We're working to get things back to normal as quickly as possible, and we apologize for any inconvenience."
Instagram said: "Instagram and friends are having a little bit of a hard time right now, and you may be having issues using them. Bear with us, we're on it."
Facebook has been approached for further comment.