Twitter revealed today that its alerts service is being expanded to users in the UK.  

The service allows registered Twitter users to receive notifications from credible organisations in the event of a national crisis or emergency.

The micro-blogging platform first announced the service in September and prior to today it was already available in the US, Japan and South Korea. It was developed after the Japanese tsunami in 2011 when Twitter was widely used to find information.

A total of 57 organisations have already signed up to the UK Twitter alerts service, including the country's 47 police forces, the London Fire Brigade, the Mayor of London's office, the Foreign Office, the Child Exploitation and Online Protection agency (CEOP) and the Environment Agency.

Those organisations that have registered for the alerts service will be able to assign an orange bell next to their Tweets when they write “#alert” as part of their 140-character Tweet.

Twitter users who follow an organisation that Twitter has verified to use its alerts service will be sent a text message in the event of an emergency, while those who have downloaded the iOS or Android app will also receive a push notification.

The Environment Agency said: "We will only use Twitter Alerts to share urgent information about a significant risk to life or the environment as a result of flooding or an environmental incident."

Commander David Martin, who is in charge of emergency planning for the London Metropolitan Police Service, said: "Getting fast and accurate information to the public in a major incident or terrorist attack really could make a life-saving difference.

"Using social networking sites, including Twitter, gives us additional ways to talk directly to the public. Twitter Alerts means that our messages will stand out when it most matters."

To subscribe an account to the Twitter Alerts service, you can go directly to an accounts alert setup page at[username]/alerts. For example,

Koby Amedume of SMS technology provider Acision welcomed the news, saying: "Every mobile phone (smart or feature) is capable of receiving an SMS via the operator or cell broadcast. Quite simply, this means it is better placed to reach more individuals than other methods including IP or internet based applications."

Twitter has 232 million monthly active users and the company says 500 million tweets are sent a day.