Popular social network sites Facebook, Instagram and WhatsApp have been hit by outage worldwide.
Users took to Twitter to raise concerns over their inability to access the Mark Zuckerberg-owned sites and apps shortly after 2pm on Sunday.
Many of the users said they could not login or send messages.
Mr Zuckerberg has not yet issued a statement to inform the sites and apps users, who run into billions, why their systems are offline.
According to âDown For Everyone Or Just Meâ, a website which helps online users check whether a certain website is down or not, both Facebook.com and Instagram.com registered downtimes while messages on WhatsApp could not go through.