The BlackBerry network is understood to be in the middle of a critical infrastructure outage, potentially affecting millions of users around the globe.

Calls to Research In Motion (RIM) have so far gone unanswered but the widespread service outage is reported to be affecting subscribers in the western hemisphere. It is understood to be affecting the sending and receiving of emails and in some cases, web browsing.

The problem is believed to have started late Tuesday following a software update on back end systems over the weekend, compounded by a database failure.

Reports suggest the system has been rolled back and RIM is in the process of trying to normalise the message queues, which may take some time.