Research in Motion on Wednesday said quarterly profit and revenue rose but the results lagged expectations and the shares tumbled even as profit margin for its BlackBerry smartphones topped forecasts.

Profit rose to $710.1 million, or $1.27 a share, in the three months ending February 27, from $628.4 million, or $1.10 a share, in the same period last year. Gross margin was 45.7 percent and it shipped 10.5 million devices.

Revenue increased 18 percent to $4.08 billion.

The results were on the light side of analyst expectations for a profit of $1.28 a share and revenue of $4.3 billion, according to Thomson Reuters I/B/E/S. It was not immediately clear if the average profit estimate was directly comparable to the figure reported by RIM.

Results from the Waterloo, Ontario-based company are under close scrutiny for the average selling price and gross margins. Some analysts fear that as RIM moves further into the mainstream market it will sell more low-end phones, which will squeeze its profitability.

For the upcoming fiscal first quarter, RIM said it expects earnings per share of $1.31 to $1.38 and revenue of $4.25 billion to $4.45 billion. It expects to add between 4.9 million and 5.2 million subscribers and have a gross margin of 44.5 percent.

U.S.-listed shares of Research in Motion fell 6.7 percent in extended trade on Wednesday after the BlackBerry maker posted its results.

(Reporting by Susan Taylor; Editing by Frank McGurty)

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