A series of distributed of denial of service attacks aimed at Sweden's transportation services caused train delays and disrupted over travel service earlier this week.

The first attack took place on October 11, striking the Sweden Transport Administration (Trafikverket) via its two internet service providers, TDC and DGC. The DDoS bombardment reportedly crashed the IT system that monitors trains' locations and tells operators when to go or stop. It also took down the federal agency's email system, website, and road traffic maps. 

Customers during this time were unable to make reservations or receive updates on the delays, BleepingComputer reported, citing local Swedish press. 

"The overload affected all our web-based systems, from train traffic to website and Skype and other systems. Now we make sure everything is working properly and, of course, review how to do it again," said Sven Lindberg from Trafikverket's press department, according to Computer Sweden.

As a result, train traffic and other services reportedly had to be managed manually, using back-up processes.

The next day, a second DDoS attack impacted the website of the Swedish Transport Agency, a separate governmental body responsible for regulating and inspecting transportation systems. It also hit Western Sweden public transport operator Vasttrafik, reportedly crashing its ticket booking app and online travel planning service.