Blackberry-maker Research in Motion (RIM) on Thursday posted a quarterly loss, due to falling revenues on the back of weak smartphone shipments.

The Waterloo, Ontario firm posted a net loss of $125 million for its fiscal fourth quarter to March 3, compared with a profit of $418 million a year earlier. Revenues fell to $4.2bn from $5.2bn.

The company said it would refocus on the corporate market rather than on individual consumers.

It also announced the resignation of former co-chief executive Jim Balsillie.

Chief technology officer David Yacht will also be standing down.

Shipments of BlackBerry smartphones in the quarter fell to 11.1 million, down 21% from the previous three-month period. Shipments of the company''s PlayBook tablets hit 500,000, largely due to substantial discounting.

For the full financial year, the company made a net profit of $1.2bn, down from $3.4bn in the previous year.

The results were worse than analysts had expected and RIM shares fell sharply in after-hours trading.

Newly-appointed chief executive Thorsten Heins said the company would now focus on its traditional core market of corporate customers rather than on individual consumers as part of a strategy to turn the business around.

"We plan to refocus on the enterprise business and capitalise on our leading position in this segment," he said.

"We believe that BlackBerry cannot succeed if we tried to be everybody's darling and all things to all people. Therefore, we plan to build on our strength."