Facebook said it suffered a self-inflicted outage lasting an hour on Tuesday that made its site inaccessible to users worldwide.
The glitch reported in Asia, the United States, Australia and the U.K. affected access from PCs and Facebook's mobile app. The social media giant's Instagram service was also inaccessible.
A Facebook statement said the disruption was caused by a technical change it made to the site and wasn't a cyberattack. Lizard Squad, a group notorious for attention-seeking antics online, claimed responsibility on Twitter for the outages.
"This was not the result of a third-party attack but instead occurred after we introduced a change that affected our configuration systems," Facebook said.
The temporary loss of service may be Facebook's biggest outage since Sept. 24, 2010, when it was down for about 2.5 hours.
On its website for developers, Facebook said the "major outage" lasted one hour.
Facebook has about 1.35 billion active users and Instagram has some 300 million.
News of the Facebook outage set rival social network Twitter alight, propelling the hashtag "facebookdown" to top trend on the site. It comes ahead of Facebook reporting its quarterly earnings on Wednesday.
As access to Facebook returned, some users in Asia reported that the site was loading slowly or not offering full functionality.
Lizard Squad on Monday claimed responsibility for defacing the Malaysia Airlines website and has said it will release data from the airline. The group has claimed responsibility for a variety of hacks over the last year, most of them aimed at gaming or media companies.