The UK conducted its first test of a new emergency alert service on Sunday, with millions of mobile phones emitting a loud alarm and vibrating.

The national system, modelled on similar schemes in Canada, Japan, the Netherlands and the United States, aims to warn the public if there is a danger to life nearby but has generated criticism over "nanny state" intrusion.

The alert was due to go off at 3:00 pm (1400 GMT), although some phones sounded the alarm before the scheduled time, and others minutes later.

Some users on social media complained that they had not received the warning at all.

The alarm was accompanied by a message reading: "This is a test of Emergency Alerts, a new UK government service that will warn you if there's a life-threatening emergency nearby."

Emergency services and the government hope to use the system to alert people to issues such as severe flooding and fires.

The 10-second alarm, which sounded even if phones were on silent, rang out at entertainment and sporting events, including Premier League football matches.

Organisers of the World Snooker Championship paused play just before the alert, while the Society of London Theatre advised its members to tell audiences to turn off their phones.

Drivers were warned not to pick up their phones during the test, and people who did not wish to receive the alerts were able to opt out in their device settings.

"Keep Calm and Carry On. That is the British way and it is exactly what the country will do when they receive this test alert at 3:00 pm today," said Deputy Prime Minister Oliver Dowden before the test.

"The government's number-one job is to keep people safe and this is another tool in the toolkit for emergency situations." (AFP)