Research In Motion has parted ways with a senior executive involved with the company's move into cloud-based services, adding to a string of high-level departures from the BlackBerry maker.

Jim Tobin, senior vice-president for software and business services reporting directly to co-CEO Jim Balsillie, left the Canadian company months ago, RIM confirmed on Thursday in an email. It has never officially announced the departure.

His exit further depletes a management team that has lost a number of top executives in developer relations, sales, and marketing in recent months.

The attrition comes as the smartphone maker struggles to regain its competitive edge against Apple Inc's iPhone and iPad and a slew of devices using Google's Android software.

RIM has repeatedly delayed its new product releases, and once launched, some of its devices have received poor reviews. Earlier this month a global outage knocked out service for tens of millions of BlackBerry users across five continents.

In July RIM said it was slashing about 11 percent of its workforce because of falling sales and profit.

Tobin was responsible for a recent move by RIM into cloud services - allowing its enterprise customers to use servers hosted by RIM instead of on-site computers to handle email and other corporate data.

He also worked on a team that developed BBM Music, a song-sharing service run on top of RIM's popular BlackBerry Messenger application as well as a wider push to incorporate Messenger into third-party developer applications.

Tobin previously worked in product development at Comcast, and at Time Warner in a corporate technology role. He was an associate principal at consulting firm McKinsey, according to his LinkedIn profile, which still shows him as a RIM employee.

RIM has parted ways with a string of high-profile employees in recent months, including chief marketing officer Keith Pardy and head of developer relations Tyler Lessard.

One of RIM's three chief operating officers, Don Morrison, resigned in July after taking a medical leave.

Two members of Pardy's team later left for jobs with rival Samsung, while a member of Lessard's developer outreach unit, Mike Kirkup, resigned in August.

A growing chorus of investors and analysts are calling for a shake-up at the very top of the company, where co-founder Mike Lazaridis and long-time partner Jim Balsillie share roles as chief executives and chairmen of the board.

RIM's shares have lost some 70 percent of their value since a peak around $70 reached in February. They were trading 2.5 percent higher at $21.24 on the Nasdaq by early afternoon on Thursday.

(Editing by Frank McGurty)