Robert Boyle Microsoft's Windows Phone 7 operating system has lured an increasing number of application developers since the software maker announced a partnership with Nokia last week, according to analytics firm Flurry.

In the four days after the February 11 deal, 4 per cent of new app projects started were for Windows Phone, compared with 1 per cent in the previous four days, according to data from Flurry, which tracks mobile games and programs.

New projects for Windows Phone passed Research In Motion's BlackBerry and now rank third behind new apps for Apple's iOS and Google's Android, Flurry said. Microsoft, which agreed last week to have its Windows Phone software power Nokia handsets, is working to turn around market-share losses to Apple and Google.

A wide variety of applications is critical to attracting mobile phone users.

Apple's software for the iPhone was the platform for 69 per cent of apps started in the 4 days after February 11. Android had 25 per cent. BlackBerry was fourth with 2 per cent.

Flurry predicts most developers will build apps for three operating systems, meaning RIM and Microsoft are likely to compete for the No 3 spot, Peter Farago, vice-president of marketing at Flurry, said in an email.

Crowdbeacon, maker of an app that lets users ask questions about nearby businesses, is now planning to release a Windows Phone 7 version, lured by Nokia's international position, said Robert Boyle, the company's chief executive officer.

The Crowdbeacon program, which lets customers ask things like where to get a haircut nearby in the next 45 minutes, now is focused on the US.

A planned international expansion means Nokia customers are a key audience, Boyle said.

"We weren't even considering it before," he said of Windows Phone 7. "It just lags behind in users in the US. The Nokia deal changed that." The Crowdbeacon app was released a week ago for Apple's iOS.

The reported surge in interest in Windows Phone comes on top of an increase that started showing up early last week as speculation about the deal mounted, Flurry reported.