Nokia's flagship Windows Phone 8 smartphone, the Lumia 920, is selling strongly across all regions, with some already speculating that it may become a threat to Apple's iPhone 5 and the Samsung Galaxy S3 - the two top selling handsets in the market.

As early as November 20, the device was all but sold out on AT&T and Amazon -the latter, for example, had the device backordered for two weeks.

Previously, there had been reports that the device had quickly sold out in the UK and Germany, and that it was in short supply in Italy, suggesting that the handset could revive the fortunes of Nokia.

The Finnish company was once the biggest mobile phone manufacturer in the world, but has struggled to compete in an era of smartphones dominated by Apple and devices running Google's Android.

Nokia has all but staked its future on the Windows Phone operating system after abandoning its own Symbian based devices last year.

A 4.5-inch handset featuring a 1280x768pixel display, 1.5GHz dual-core processor and 1GB RAM, the Lumia 920 is certainly one to be taken seriously.

One of the first on the market, alongside HTC's 8X to run Windows Phone 8, the handset is also crucial for Microsoft gaining a foothold in the smartphone sector where it too has lost considerable ground to Google and Apple. In many ways both companies are relying on each other in developing the Windows Phone 8 handset, but some analysts are insisting that reports of the smartphone's success should be taken lightly.

For example, Deutsche Bank analyst Kai Korschelt told Street Insider that recent press reports on Lumia selling out are "misleading."

The firm's retail and industry research indicates the device is only selling out because of limited device supply, rather than overwhelming demand.

"Anecdotal evidence suggests that many stores have only received 5-20 devices per store with wider carrier distribution delayed in some countries such as Germany and UK," said Korschelt.

What's worse, Deutsche Bank says that surveys in the UK suggest less than 10% market share in the first weeks post launch, which is lower than the Lumia 800 launch one year ago.

"Our analysis suggests current consumer interest could drive potential Lumia shipments of 5-6m per quarter next year, well below consensus expectations of 30-35m units for 2013," says Deutsche Bank.

These figures suggest, while the Lumia 920 is probably the most exciting device to come out of Nokia for years, it still has a lot of work to do before it turns around the company's fortunes.