Nintendo has now updated its status messages in North America and Europe to state that its network services are once again operating normally, after a downtime of one hour and 25 minutes.
In the case of Wii U, 3DS and DSi these technical difficulties are related directly to the eShop and DSi Shop platforms, whereas the Wii system is affected in both the Wii Shop and broader network services. In terms of both updates the error occurred at the same time — 16:20 UK time / 08:20 Pacific / 11:20 Eastern. At the time of writing the UK status page says that services are suspended, but in North America "some online service features may be unavailable".
We've been able to access the Wii U eShop just fine at the time of writing, but the issue may be related to purchasing content; there's no scheduled maintenance listed for this period.
We'll update this article once the status pages are updated, but have you noticed any issues in your regions?
Thanks to WiiLovePeace for the tip.