Facebook announced on Tuesday that it was rolling out a tool that aims to provide users with potentially life-saving information in emergencies, as it seeks to improve its public image and play down its reputation as a network that aids the spread of misinformation.

Local Alerts, which it has been testing since last year in 300 cities including Charlotte, St. Louis and Miami and now plans to offer across the United States, is intended to provide reliable information to people caught up in events such as mass shootings and extreme weather, it said in a blog post.

Alongside other social media companies, Facebook has faced a barrage of international criticism for the way its platform has been used to spread conspiracy theories and extremist views and it is keen to focus attention instead on its role as a connector of friends and family.

The world's largest social media network already offers users the ability to let friends know they are safe during emergencies with a feature called Safety Check, but said it wanted to do more.

With Local Alerts, Facebook account holders in local government and among first responders such as the police and fire departments can send out messages that are then spread more widely by Facebook.

It was not immediately clear how useful the service was in its pilot phase. When asked if Local Alerts to date have been deployed quickly enough to make a difference or have been employed in situations where users were in danger, Facebook declined to give examples, citing the privacy of its account holders.

It also said the speed at which alerts were disseminated was dependent on the account holders.

In one example, when a disgruntled student opened fire during the last day of classes at the University of North Carolina at Charlotte in April, the City of Charlotte Government's Facebook page sent a Local Alert notifying nearby residents when it was safe to return.

The alert was posted more than two hours after the shooting, said Ken Brown, Charlotte's Interim Media Relations Manager.

Some local authorities contacted by Reuters said they were using Local Alerts alongside other services to warn citizens of danger. Mt. Juliet Police Department in Tennessee said it uses a combination of Facebook Local Alerts, mobile text messages through the Nixle platform, and posts on local community media service Nextdoor to send emergency notifications.

The local authorities said they had sent alerts over emergencies including road closures, bad weather, and missing people.

"I grew up in Kansas and this is the time of year when we get a lot of tornadoes," Jimmy O'Keefe, Facebook's head of Product Marketing for News Publishing, said. "This tool would have given us a lot of peace of mind if it was around back then."