Microsoft released its first sales figures on Tuesday for new Windows Phone 7 smartphones, saying more than 1.5 million of the handsets were sold by manufacturers in the first six weeks.
Achim Berg, vice president of business and marketing for Windows Phones, said sales were "in line with our expectations - especially when compared to other new platform introductions."
"We are pleased that phone manufacturers sold over 1.5 million phones in the first six weeks, which helps build customer momentum and retail presence," Berg said in a statement.
Microsoft unveiled the latest version of its mobile phone operating system in October as it seeks to claw back lost market share from Apple's iPhone, the Blackberry and devices powered by Google's Android software.
South Korea's Samsung and LG Electronics, Taiwan's HTC and US computer giant Dell are among the companies manufacturing Windows Phone 7 handsets.
The new device launched in Europe and the Asia Pacific region on October 21 and in the United States and Canada on November 8.
"Several more mobile operators around the world will introduce Windows Phone 7 on their network in 2011 and we will have a broader portfolio of devices from phone manufacturers at different price points," Berg said.
"We know we have tough competition, and this is a completely new product," he added. "We're in the race - it's not a sprint but we are certainly gaining momentum and we're in it for the long run."
Berg also said more than 18,000 software developers were making applications for Windows Phone 7 handsets and 4,000 applications were currently available.
Microsoft's share of the global mobile operating system market will fall to 4.7 percent this year from 8.7 percent last year, according to Gartner, a technology research firm.
Apple sold more than three million iPhone 4s in the first three weeks after its debut earlier this year, its most successful product launch ever.
Finland's Nokia still leads the worldwide market, with 29.5 million smartphones sold during the third quarter of the year for a 36.6 percent share, down from 44.6 percent a year ago, according to Gartner.
Sales of Android-powered smartphones meanwhile soared to 20.5 million units, giving the Android platform a 25.5 percent market share, up from just 3.5 percent a year ago, Gartner said.
Google said this month that more than 300,000 smartphones running its Android software are being activated daily.
Apple's iPhone came in third on Gartner's list, with sales of 13.5 million units for a 16.7 percent market share, down from 17.1 percent a year ago.
Canada's Research In Motion, maker of the BlackBerry, was in fourth position with sales of 11.9 million units. Its market share dropped to 14.8 percent from 20.7 percent a year ago.
Microsoft's Windows Mobile saw sales of 2.2 million units, giving it a 2.8 percent market share, down from 7.9 percent a year ago, Gartner said.