At this point there is no information regarding when exactly it's expected to be fixed, but everything will be done to fix it as soon as possible.
You can expect a more official announcement regarding this later on today, that contains more information.
Issues with the same symptoms have been fixed during a maintenance before, thus I think that the chances are high that there will be one.
We'll keep you updated as soon as we know more.
Have a good day/night.
Update 2: The server is back up, and the issue is probably fixed.
Edited by VanillaPudding, 23 June 2016 - 12:40 PM.