Research In Motion has unveiled the smallest BlackBerry device to carry a full keyboard so far as it tries to secure more of the smartphone market ahead of an assault on the sector by Apple’s iPhone.

The new BlackBerry Curve is fitted with a two-megapixel camera with a built-in flash and a full-screen viewfinder – and a photo-editing feature. When its users aren’t playing music and videos (it has a 3.5mm stereo headset jack), they can even make voice calls and send e-mails.

The device, due for release this spring in the US, will aim to build on the success of the BlackBerry Pearl, which was launched last September. The Pearl has proven popular, although it did not carry a full “Qwerty” keyboard like its forebears.

Like the Pearl, the Qwerty-equiped Curve is aimed at bridging the gap between professional users and consumers - the so-called “prosumer” market.

It comes as RIM looks to build its user base amid heightened competition in the smartphone sector. It recently unveiled plans to expand its BlackBerry mobile e-mail service beyond its current 8 million subscribers by opening it up to rival devices that run on Microsoft’s Windows Mobile 6.0, a specialised operating system.

The move, also designed to boost the BlackBerry network's credentials as a consumer service, and not just a tool for deal-making lawyers and bankers, came as mobile services fast emerge as the next battleground for internet groups.

Apple's iPhone, for instance, will offer a free "push" e-mail service from Yahoo!. At the device's launch in January, Jerry Yang, the Yahoo! co-founder said: "It's basically like having a BlackBerry."

Apple is targeting sales of 10 million iPhones after the gadget's US launch, slated for June. Its European debut is planned for the autumn.

RIM has not announced a price for the Curve. It is expected to cost about $200 (£100) in the US – though mobile operators are likely to heavily subsidise the device and offer it for free with some contracts.

The device, weighing 110 grams, is 10.6cm long by 6.1cm wide, and 1.52cm deep.

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