Nokia will reportedly unveil three new handsets running the Windows Phone OS this week, representing the first fruits of a tie up with Microsoft that will see Nokia focus on Windows Phone for its smartphone devices.

Leaked details obtained by suggest the devices – called the Nokia 800/SeaRay, Ace and Sabre – will be announced on Wednesday at the Nokia World event in London.

All three devices will run the Windows Phone 7.5 or Mango version of the OS and be available to buy by mid-November, according to reports.

The SeaRay device will be available in pink, light blue or black casing, similar in design to the existing Nokia N9 smartphone, according to leaked press shots. It will have a 3.7 inch curved screen and 8MP camera.

The Sabre reportedly has a 3.5 inch screen and a 5MP camera while the more business-focused Ace has a sliding screen that reveals a keyboard, an 8MP camera, and will be available in black or silver.

Speaking at the Web 2.0 conference in San Francisco last week, Microsoft CEO Steve Ballmer said Nokia will unveil “a bunch” of new Windows Phone devices this week, while Windows Phone Andy Lees also indicated this would be the case when speaking at the AsiaD conference in Hong Kong.

Nokia’s Q3 2011 results revealed that the company’s smartphone revenue fell by 39 percent during the period, with volumes decreasing by 38 percent. Apple and Samsung meanwhile continued to strengthen their hold on the market and so Nokia will be hoping the alliance with Microsoft will help reverse this trend.