UPDATED 7.58pm: Civil Defence has set up a survey for feedback on its mobile emergency alert test.

The test alert was issued just after 6 this evening.

Civil Defence is now asking people to let them know whether they received it or not, in a survey on its website.

There's also a checklist helping people find out if their phone is capable of receiving the alerts.

It was expected that around a third of phones would immediately be able to receive alerts, but Civil Defence says this will rise over time.

The alerts are sent using cell broadcast technology and you can't opt out.

"There's no need to sign up or download an app - all you need is a mobile phone that is capable of receiving Emergency Mobile Alerts, and a network signal," Ministry of Civil Defence and Emergency Management director Sarah Stuart-Black said.

Stuart-Black says the technology allows officials to provide timely and accurate information during a disaster.

Those people whose mobile phones are capable of receiving the alerts can expect to hear a loud, penetrating sound, and a notification will display.

It's designed to send information to mobiles in a defined area, if there's an imminent threat to life and property.

The system was accidentally triggered last month, waking thousands of people in the middle of the night.

Sarah Stuart-Black says changes have been made to prevent a repeat of that.