Spanish daily El Pais reports significant ongoing disruptions to travel, with airports, trains, metros and traffic lights affected by the blackout.
Businesses have also been severely impacted, with Anadolu confirming that at least some oil refineries have shut down.
Authorities are investigating the causes of the outage. Spain's National Institute for Cybersecurity is also studying whether a cyberattack could be responsible.
Spain’s national electricity provider said it is working to restore service.
More than 40 minutes after the initial outage, large swathes of Spain remain without electricity.
Communication is also being disrupted, with telephone services reportedly collapsed, although 5G networks are functioning intermittently.
AzVision.az