BlackBerry BBM for Android, iPhone - Free download now... if you've signed up

6 million Android and iPhone customers pre-register for launch

BlackBerry said on Monday it has begun to roll out its much-awaited BlackBerry Messenger (BBM) service for users of Android and iPhone devices.

The long-awaited cross-platform offering, which was delayed after issues arose following the initial launch last month, is now being rolled out in a phased manner.

"To help manage this unprecedented pent-up demand for BBM, we are implementing a simple line-up system to ensure a smooth rollout," Andrew Bocking, who heads the BlackBerry's BBM business, said in a blog post on the company's website.

Read More