Social networking company Facebook has launched a free messaging service called Facebook Messenger.

The company launched the app for users in the US. It allows Facebook account holders to send instant messages on their mobile phones – both Android and Apple — to contacts on their ‘friends’ list.

The app will compete against a similar service offered by BlackBerry – Blackberry messenger (BBM), which shot to limelight for its role in the London riots.

BBM is said to have over 45 million users, while Facebook has said that it has a user base of more than 750 million users worldwide on the social networking site.

Earlier this year, Google’s latest social networking offering Google+ had introduced Huddle, which is a messaging service and reports say that Apple would be releasing its iMessage later this year.

Facebook engineer Lucy Zhang wrote in a blog post that it isn’t always easy to know the best way to reach someone on their phone.

Zhang added, "Should you send an email or text? Which will they check first? Did they even get your last message?"

"We think messaging should be easier than that. You should be able to write a message, click ‘Send’ and know that you will reach the person right away."

It is unknown when the service would be made available for users outside the US.