Research In Motion (RIM) on Wednesday announced that the US Department of Defense staff and partners have been given the go-ahead to use more of the Canadian firm's BlackBerry OS 7 smartphones.

Combat support group Defense Information Systems Agency tested BlackBerry smartphones running on the mobile software platform, which is to be replaced later this year with BlackBerry 10.

Army lab testing ended with the department adding the BlackBerry Bold 9900 and 9930; the BlackBerry Torch 9810, 9850 and 9860, and the BlackBerry Curve 9360 to its list of approved handsets, RIM said in a release.

The BlackBerry system 7 will allow military and other Defense Department users to get higher levels of performance from a wide range of applications and smartphone capabilities added in the past year, the company said.

Enhanced features included voice-activated search and near-field communication (NFC) technology that allows smartphones to be used for payments at checkout counters, according to RIM vice president Scott Totzke.

The company's focus on keeping BlackBerry communications secure was cited as a priority for the military.

"RIM's unwavering focus on security and RIM's achievement of key security certifications...continue to be very important to many of our DoD and enterprise customers," Totzke said.

The announcement came a month after the Waterloo, Ontario-based company announced a loss last quarter amid lower than expected sales of its BlackBerry, which has been losing ground to Apple iPhones and smartphones powered by Google-backed Android software.