Research In Motion posted a 27 percent drop in quarterly profit on Thursday and said it would ship between 11 million and 12 million BlackBerry smartphones in the weeks around Christmas, the first decline in years for that historically strong period.

RIM's already depressed shares shed more than 6 percent in brisk after-hours trade as investors focused on the lacklustre outlook for shipments and the high cost the company was paying to stick with its poor-selling PlayBook tablet.

RIM turned in a sharp drop in adjusted profit at $667 million (429.96 million pounds), or $1.27 a share, in its third quarter ended on November 26. That does not include a massive writedown on unsold PlayBooks or a charge associated with October's global service outage.

It generated revenue of $5.17 billion, compared with $5.5 billion a year earlier.

Analysts on average had expected RIM to earn $1.19 a share on sales of $5.265 billion after the struggling Canadian company warned on profit, revenue and shipments on December 2.

In the third quarter a year earlier, RIM made $911.1 million, or $1.74 a share.

The intervening year has been mostly downhill for RIM, which made its name with secure, reliable communications for the world's business and government elites before branching out into a now crowded consumer market.

For the current quarter, RIM expects to make between 80 and 95 cents a share on revenue of between $4.6 billion and $4.9 billion.

The Waterloo, Ontario-based company has failed to match the popularity of Apple's iPhone and iPad or the slew of devices from the likes of Samsung and HTC Corp that make use of Google's Android software.

Including the $485 million pre-tax writedown on discounted PlayBook inventory and a $54 million charge related to the outage, RIM made a third-quarter profit of $265 million, or 51 cents a share.

(Reporting by Alastair Sharp)