Worldwide sales of mobile phones fell 6.1% overall in the second quarter of this year, but this drop disguised the phenomenal growth of the smart phone market which increased 27% of the same period last year.

Gartner said the smart phone segment remained the most attractive for manufacturers as it was far more resistant to the thinning margins of the midtier and low-end sectors, with 41 million units sold.

The largest smartphone manufacturer remained Nokia, with more than double the market share of nearest competitor Research in Motion. Apple maintained third position, but grew its market share from 2.8% to 13.3% compared to the same quarter last year due to the release of the iPhone 3GS.

"Manufacturers must offer products with the features that consumers and operators are demanding most strongly, like touchscreens, focus on user interfaces and application/content ecosystems, and work hard to keep operators loyal," said Gartner research director Carolina Milanesi, adding that operators were likely to drive competition in the mobile sector by offering e-book readers and mini-notebooks to boost mobile broadband subscriptions.