Facebook users in Hong Kong feared a 30-minute blackout yesterday was part of cyberattacks that have been linked to the Occupy Central movement.
The social media giant went down across the world at about 3.50pm Hong Kong time, setting off a flurry of panicked messages on other social media.
Users who tried to log into Facebook received an error page that simply said: "Sorry, something went wrong. We're working on getting this fixed as soon as we can."
Hong Kong users speculated on Twitter that there had been a distributed-denial-of-service attack, similar to recent attacks on the website of newspaper Apple Daily - known for its pro-democracy stance - which resulted in only limited access to its online editions on Wednesday.
The popvote.hk  website, built by the University of Hong Kong and Polytechnic University, has sustained similar attacks ahead of Occupy Central's "referendum" on electoral reform, which begins today and will finish on June 29.
"#Facebookdown is big deal in jittery #HK," wrote former journalist Yuen Chan, on Twitter.
Others were not so concerned, and made jokes about the blackout.
"Don't be afraid, those strange noises you are experiencing are other people talking to you. #facebookdown," tweeted Markus Beyer.
In a statement the California-based company said: "Earlier this morning, we experienced an issue that prevented people from posting to Facebook for a brief period of time. We resolved the issue quickly, and we are now back to 100 per cent. We're sorry for any inconvenience this may have caused."
The company did not explain the reason for the lost service.
Facebook's last substantial blackout came in 2010, when it went down for more than two hours due to a server error that could only be fixed by turning off its site to reduce traffic loads.
Facebook, which had more than two billion active users in March, is one of the world's most-accessed internet services.
News of the blackout spurred the hashtag Facebookdown to be referenced on Twitter more than 49,000 times within an hour, according to Topsy, a US social media analytics company.
Meanwhile, users of the popular mobile messaging app Line have been told to change their passwords after 303 cases of unauthorised access in Japan were confirmed between late May and June 14, including three that involved cash trades resulting in financial losses. Line said the problem was not with its security but with users failing to take care of their passwords.