Social network website Facebook, which has around 850 million users worldwide, went down in several mainly European countries on Wednesday for around two hours, users and the company said.
"Today we experienced technical difficulties causing the site to be unavailable for a number of users in Europe," Facebook said in a statement.
"The issue has been resolved and everyone should now have access to Facebook. We apologise for any inconvenience."
The outage affected facebook.com as well as its apps for mobile phones and tablets.
As a result, #facebookdown was the top trending hashtag in France on microblogging site Twitter on Wednesday.
The outage could be a result of a disconnect with Facebook's servers holding users' personal data.