A siren has sounded on smartphones across the UK as part of a government test of a system that will be used to warn of life-threatening emergencies

However, initial reports suggest many people didn't receive the alert and for some people it sounded earlier than expected

The Three network has said it is aware "that a number of customers" were affected and didn't receive the notification

It's designed to be used for serious weather-related events, such as severe flooding, fires and extreme weather and may also be used during terror attacks

Cabinet minister Oliver Dowden said it will be used only in situations where there was an immediate risk to life

The test had originally been planned for the early evening but was moved to avoid clashing with an FA Cup semi-final at Wembley Stadium, which kicks off at 16:30