A fault in Microsoft's Azure cloud computing platform has knocked some customer sites offline, with issues being felt globally according to the software's status page.
Azure works by allowing smaller third-party businesses to rent servers and computing power from Microsoft rather having to manage their own.
According to Azure's official logs the issue started shortly after midnight, with European customers being those taking the longest to get back online.
The Azure status page has since updated to say that "everything is running great", but some sites have remained offline. Other sites have reappeared.
Microsoft Office 365 and Xbox Live services are also said to have been disrupted.
This sort of server outage is not uncommon among cloud platforms, but it comes at an unfortunate time for Microsoft, as it has recently increased advertising of the service in an attempt to keep up with the likes of Amazon and Google, who offer their own versions of the service.
On the service level agreements page of the official Azure website, Microsoft guarantee service availability "at least 99.9%" of the time.
The issue has so far been put down to a glitch by security experts, with no suggestion of a hack or attack against Microsoft.
Mark James, security specialist at online security firm ESET said: "At first glance it appears nothing more than a hardware or software fault, I see no mention of DDOS attack but we won't know until Microsoft releases a full report after the event has been resolved. This highlights one of the problems with the movement towards cloud hosting - when we put our faith in the internet to store our data or provide our business apps then we have to expect that sooner or later it's not going to be available.
"When we move towards a cloud solution we have to understand our data is being hosted on someone's else's servers using someone's else's IT team and relying on their ability to fix any situation and more importantly releasing information as quickly as possible to affected customers."
Microsoft is yet to officially comment on the issue.
Tim Erlin, director of security and risk at software firm Tripwire added: "Azure isn't the only cloud provider to have experienced an outage, but the scale of this incident certainly makes it notable. Unfortunately for Azure customers, there's little information to be had from Microsoft on why this outage occurred other than that '[t]his incident has now been mitigated'.
"If Microsoft wants to ultimately mitigate the potential business impact from this outage, they'll need to provide more transparency to customers on what happened and why it won't happen again."