BlackBerry maker Research in Motion’s sales figures for the most recent quarter fell short of investment analysts’ expectations, causing the company’s share price to drop by 15%.

RIM reported quarterly revenues of $4.9 billion, up 16% year-on-year but down 12% compared to the immediately preceding quarter.

This drop in consecutive sales will have been especially disappointing for the company, as it launched its PlayBook tablet device in the US during the quarter. RIM says it shipped 500,000 of the devices, although it is not known how many have actually been bought by end users.

The company’s net income for the quarter was slighly above analyst expectations, however, at $695 million.

“Fiscal 2012 has gotten off to a challenging start," said RIM co-CEO Jim Balsillie, warning investors to expect more of the same in the next quarter. "The slowdown we saw in the first quarter is continuing into Q2, and delays in new product introductions into the very late part of August is leading to a lower than expected outlook in the second quarter."