Alan Brenner, a senior vice president for the BlackBerry platform, will leave after a transition period, and Alistair Mitchell, a vice president for the BlackBerry Messenger instant messaging product, has already left, RIM spokeswoman Tenille Kennedy said in an email on Friday.

A stream of executives have left RIM in the past year as its once-dominant market share has slipped amid fierce competition from Apple Inc and phones running on Google Inc's Android. RIM shares have dropped more than 80 percent from a peak of almost $70 in February 2011, to $12.67 on Nasdaq on Thursday.

Last week, RIM said it would stop issuing financial forecasts and that it was reviewing strategic options, such as entering partnerships and joint ventures or licensing its software.

CEO Thorsten Heins, who took the reins in January when longtime co-CEOs Mike Lazaridis and Jim Balsillie resigned under pressure, would not rule out a possible sale of the company.

Several senior executives announced their departures in last week's earnings report - including Balsillie, who stepped down from the board. RIM posted a net loss of $125 million after booking writedowns on its legacy BlackBerry 7 phones and goodwill.

RIM last recorded a loss under generally accepted accounting principles (GAAP) in the fiscal 2005 fourth quarter, when it booked tax expenses and paid to resolve a patent infringement case that had threatened to shut down its U.S. operations.

The Waterloo, Ontario-based company is seeking a chief marketing officer and a chief operating officer.

In July RIM slashed 2,000 jobs, or about 11 percent of its workforce, to cut costs as sales and profit fell. [ID:nL3E7IP251] Its developer relations and sales and marketing teams were particularly hard hit.

Head of marketing Keith Pardy left in March 2011, just before RIM launched its PlayBook tablet, which fared poorly. Two of his staff later moved to Samsung Electronics.

Chief Operating Officer Don Morrison resigned in July after taking medical leave. A second COO, Jim Rowan, left last week along with Chief Technology Officer David Yach.

Jeff McDowell, senior vice president for platform marketing and alliances, left RIM last July and Tyler Lessard, a senior vice president for global alliances and developer relations, left in September.

(Reporting by Alastair Sharp in Toronto; Editing by Richard Chang)

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