Apple's iPhone is still outselling handsets running Google's Android platform, says Gartner.

According to market research company, in the smartphone OS war, Android and Apple were the winners in the first quarter of 2010.

It was Apple's strongest quarter yet, as sales to end-users increased by 112.2 percent to 8.3 million units.

Android's momentum continued into the first quarter of 2010, particularly in North America, where sales grew 707 percent compared to the same period last year.

Sales of Android phones grew from 575,000 to 5.2 million units.

The reason for Apple's three million unit lead is that the iPhone is more popular than Android-based devices in Europe and Asia, according to Carolina Milanesi, research vice president at Gartner.

In Europe, there were about twice as many iPhones sold as Android-based smartphones during the first quarter, she said.

Overall, smartphone sales to end users increased at the fastest rate since 2006, growing by 48.7 percent to 54.3 million units, Gartner said.

Symbian is still the largest smartphone platform by a wide margin, helped by sales of cheap smartphones from Nokia, but the platform is not growing as fast as the competition.

Sales totaled 24.1 million units, up from 17.8 million a year earlier, but Symbian's market share slipped from 48.8 percent to 44.3 percent.

Research In Motion (RIM) is in second place, but like Symbian its market share dropped, from 20.6 percent to 19.4 percent. However, sales of 10.5 million units made RIM the fourth-largest mobile phone manufacturer in the world.

Apple's iPhone OS is still the third-largest smartphone platform, but Android has now moved passed Windows Mobile for the first time, taking the fourth spot.

The Android and iPhone platforms grew their respective market share, iPhone OS from 10.5 percent to 15.4 percent and Android from 1.6 percent to 9.6 percent.

Sales of smartphones based on Microsoft's Windows Mobile stayed at about 3.7 million units, with market share dropping from 10.2 percent to 6.8 percent.

The arrival of phones running the Microsoft's new mobile operating system, Windows Phone 7, couldn't come soon enough for the company.

Overall, the sales of mobile phones bounced back during the fourth quarter, totalling 314.7 million units and growing by 17 percent, according to Gartner.

See also: Google Android overtakes iPhone in the US