A power cut has affected the Welsh Ambulance Service system’s ability to receive emergency 999 calls.
Patients are being urged to only use the 999 service “wisely”, and in an emergency, in order not to clog the system.
Engineers are working to resolve the problem in order to restore normal service as soon as possible.
Richard Lee, Director of Operations at the Welsh Ambulance Service, said: “Please only ring us if the situation is life-threatening, and use us appropriately.
“If you have a life-threatening emergency, you should continue to dial 999. We will answer your call and we will get an ambulance to you.
“If we dispatch an ambulance, and you’re able, it would be helpful if someone is able to wait for the ambulance in the street in order to flag it down.
“If you’re ill and unsure what to do, you can call NHS Direct Wales on 0845 46 47 or visit the website, where you’ll find a wealth of advice and information.
“Don’t forget about your GP, your nearest pharmacist or Minor Injuries Unit, where there is no need for an appointment.”