A public emergency alert will be sent to all mobile phones in the UK next month to test a new Government public warning system.
The alert system will allow the Government and emergency services to send urgent messages to warn members of the public about life threatening situations such as flooding or wildfires.
A siren-like alert will sound as part of the test which is expected to take place in the early evening of April 23.
Phone users must acknowledge the alert before they can use other features on their devices.
A siren-like alert will sound as part of the test which is expected to take place in April
PA
A message will appear on the home screen of people’s devices during the test which will cause phones to vibrate and play a loud warning sound that will ring for around 10 seconds, even if the phone is on silent.
The new system became operational on Sunday and is being based on similar schemes used in the US, Canada, Japan and The Netherlands.
Messages will only ever come from the Government or emergency services and will initially focus on weather-related events.
The emergency alert will reach 90 per cent of mobile users within the relevant area.
Terror alerts could also be introduced to the list of potential events which would trigger a notification.
Mobile phone users should expect a message with details of the area affected and instructions about how to respond.
Cabinet minister Oliver Dowden said the warnings are sent in a "very targeted way" and he hopes many users will only ever hear the test.
People can opt out by searching emergency alerts on their device and turning the severe and extreme ones off.
An emergency message will appear on all UK mobile phones as a siren-like noise sounds
Twitter/Cabinet Office
However, officials advise against turning off alerts as they could be lifesaving.
The Cabinet Office said the service will be secure, free and will not collect personal information.
The system uses cell broadcasting technology with all cell towers in a defined area broadcasting it.
Trials have already been held in Reading and East Suffolk.
National Fire Chiefs Council chairman Mark Hardingham said the new system would help fire and rescue services to do their jobs "and to help communities in the event of emergencies".