United Kingdom’s National Health Service (NHS) 111 telephone service used for medical emergencies suffered a major outage caused by a cyberattack.

According to Advanced, a firm providing digital services for NHS 111, the attack took place last Thursday and targeted the system used to refer patients for care, including ambulances being dispatched, out-of-hours appointment bookings and emergency prescriptions.

The incident impacted Advanced's Adastra client patient management solution used by 85% of NHS 111 services together with some other Advanced's services.

The UK National Crime Agency said it was “aware of a cyber incident” and was working with Advanced.

The Welsh Ambulance Services has described the outage as “significant” and “far-reaching, impacting each of the four nations in the UK.” The NHS, however, said disruption was minimal.

Advanced's Chief Operating Officer Simon Short told BBC that the incident was related to a cyber-attack and “as a precaution, we immediately isolated all our health and care environments,” noting that the issue had been contained “to a small number of servers.”

At present, there is not much details on the nature of the cyberattack, but security experts believe that it likely involved ransomware.