Emergency alerts which sound on mobile phones with a loud siren-like noise will be tested nationwide next month, the government has announced.

A vast trial-run of the planned emergency system – nicknamed the 'Armageddon alarm' – will set off the sirens on millions of people's devices across the UK.

The emergency alerts system, run by the government, is designed to make people aware of imminent danger through their phones and tablets.

Alerts, which are broadcast from mobile phone masts, can be activated if it is felt there is a danger to life nearby.

Phones or tablets within range will then be able to pick up and broadcast the warning, which may also come with written advice displayed on the screen as to how to stay safe and what action to take.

According to the National Resilience Framework, published by the government in December, the emergency alerts system is to be launched across the UK in 'early 2023' – but up until now the only tests of the system to have taken place happened in Reading more than a year ago with mostly Android devices.

The government confirmed last night that the national test will now take place on Sunday, April 23.

Mobile numbers are not required to send out the alerts that will automatically trigger a "loud siren-like sound", vibrate and read out the message lasting around 10 seconds at a time.

Even if the phone is set on silent the message will still sound.

However, some devices can opt out of receiving the alerts by changing the settings stored within devices.

People with phones that are incompatible with the service will still be told, with the government saying that the emergency services "have other ways to warn you when there is a threat to life".

The government advise that once you get the message, you must stop what you are doing and follow the instructions.

Those who are driving on the day should not read or respond, but continue until it is safe and legal to stop before looking at their phone.

They add: "If there is nowhere safe or legal to stop close by, and nobody else is in the vehicle to read the alert, tune into live radio and wait for bulletins until you can find somewhere safe and legal to stop."

People with vision or hearing impairment will receive audio and vibration attention signals instead.

When the service eventually goes live, households could receive emergency alerts about incidents such as severe flooding, a fire, a terrorist attack or public health emergencies, says the government guide online.

Alerts will be sent only by emergency services, government departments and other public bodies responsible for co-ordinating emergency responses in the country.

Previous tests held in Reading sent people a short message which read: "This is a mobile network operator test of the Emergency Alerts service. You do not need to take any action. To find out more, search for gov.uk/alerts."

With government plans to introduce the emergency alerts having been in place since 2013, some members of the Labour party have expressed concern at the apparent delay in fully rolling out the system since those initial tests in 2021.

In a tweet last weekend, Labour MP and shadow paymaster general Fleur Anderson said: "Mobile phone alerts are a basic service but are only now being tested.
"We could face another Covid or other emergency tomorrow and I'm worried that the government is lagging far behind on keeping our country safe."