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Apple shares have tumbled 12% as investors fret over whether the company could lose its dominance in the smartphone market.

About $50bn (£32bn) was wiped off Apple's value after the biggest daily drop in the firm's stock in four years.

Flat profits and record quarterly revenue of $55bn were not enough to overcome disappointment over sales of the company's new iPhone 5.

Analysts said the firm was in danger of becoming a victim of its own success.

Earlier, shares in some of Apple's key Asian suppliers also fell.

LG, which provides displays for Apple products, fell 3.1%, and Hon Hai, which assembles iPhones and iPads, dropped 3.2%.

Apple was unable to repeat its usual growth in profits, which were unchanged from a year earlier at $13.1bn.

The firm said late on Wednesday it had sold more iPhones (47.8 million) and iPads (22.9 million) in the final three months of last year than in any previous quarter, but investors had expected more.

Shares in the firm have fallen by a third since September over concerns the company may be losing its edge over increasingly confident competitors.

Shares currently stand at $460, down from over $700 four months ago. Apple still remains the world's most valuable company, however, just ahead of Exxon Mobil.

On Thursday, a number of brokers cut sharply their price target for the shares, with Deutsche Bank slashing its forecast from $800 to $575.

The iPhone's once dominant position is being challenged by Samsung and other makers of Android-based devices, which now make up a far greater percentage of overall smartphone sales than the iPhone.

Nokia, once itself the leading mobile phone manufacturer, reported on Thursday a return to profit in the final quarter of last year, with strong sales of its new Lumia smartphone, its first major product launch since the company teamed up with Microsoft.

With Apple no longer seen as the market leader in innovation, some analysts believe it may now have to rethink its core strategy, which is based on focusing on a handful of premium products.

"Apple's modus operandi to date has been to cream the high-end off each market, but as the company's grown it may now need to target more of the mainstream," analysts at Evercore Partners said.

Normura's Stuart Jeffrey agreed: "To re-accelerate growth, Apple likely needs to launch new products, yet few seem likely before June".

Others, however, argue that investors' expectations are wholly unrealistic, and the company remains hugely successful.