Microsoft's Windows Phone is slowly gaining on its competitors in the U.S. mobile phone market, new research revealed today.

Research group Kantar Worldpanel ComTech, which regularly publishes reports on the mobile industry, revealed some new numbers concerning the first quarter of 2013 as well as the previous year.

Though Android still holds the lion's share of the market with 51.7 percent, Microsoft is growing faster than its Google-owned competitor, with 1.8 percent growth over the last year compared to Android's 1.4 percent.

Apple's iOS, meanwhile, leads in growth with 2.3 percent but still lags behind Android with 41.4 percent of smartphone sales during the period.

The slow rise of Windows Phone

Yes, Windows Phone is still significantly behind with just 5.6 percent of the market, but at least it's experiencing healthy growth.

And Microsoft isn't likely to let it stop there - we'd be surprised if Windows Phone doesn't continue to blossom. This isn't the first we've heard of Windows' upward ways, after all.

"We're seeing increasingly high consumer demand for Windows Phones worldwide," a Microsoft spokesperson told TechRadar, citing separate research from IDC that found Windows Phone to be the fastest-growing mobile OS.

"According to IDC's latest report, Windows Phone posted the largest year-over-year gain among the leading operating systems (131 percent year over year), more than doubling its size from a year ago and leapfrogging over BlackBerry for the third place," the spokesperson said.

Unsurprisingly, Kantar Worldpanel reported that the majority of Windows' growth was driven by Nokia's flagship Lumia devices. No doubt HTC's impressive Windows Phone 8 devices, like the Windows Phone 8X, had something to do with it as well.

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According to Kantar Worldpanel's research, 42 percent of those who purchased a Windows Phone device during the first three months of the year upgraded from feature phones.

Others upgraded from other Windows Phone devices (25 percent) or from Android phones (23 percent).

It looks like that Apple brand loyalty we heard about last year is still intact, as it seems an insignificant number of iOS users switched to Windows Phone - that figure isn't even mentioned. As far as upgrades to iOS, only 31 percent came from feature phones.

"But it's not just about capturing the market that is yet to upgrade," said Kantar Worldpanel ComTech Analyst Mary-Ann Parlato. "Windows is also seeing success in the younger group."

She added that Windows Phone captured more 50- to 64-year-olds between 2011 and 2012, while in the last year the Microsoft OS gained ground with those aged 25 to 34.