* Icahn raises stake in Motorola
* NPD says Motorola Droid was Android U.S. bestseller
* Motorola shares rise 6 percent
NEW YORK, Aug 4 Shares in Motorola Inc MOT.N rose 6 percent on Wednesday after billionaire investor Carl Icahn said he had raised his stake in the company to 9.9 percent from 8.75 percent.
The news coincided with a research report from NPD that said phones based on Google Inc's (GOOG.O) Android software took the biggest share of the U.S. mobile market in the second quarter and Motorola had the top selling Android phone.
Investors took the increased investment from Icahn as a sign of confidence in Motorola's plan to split the company in two in the first quarter of 2011, according to analysts.
Motorola shares were up 46 cents to $8.08 in Wednesday afternoon trading on the New York Stock Exchange.
"Icahn's been involved for a long time. The fact he's still increasing his ownership is a positive," said Morgan Keegan analyst Tavis McCourt. "I think he's betting that the separation will create value."
McCourt said the NPD Group report also helped.
According to NPD, the top selling U.S. Android phone was Motorola's Droid, which was launched in the fourth quarter last year. HTC Corp (2498.TW) phones such as the Droid Incredible were the next best sellers.
"Droid outsold the Droid Incredible," said McCourt, "That's amazing given the Droid was a old product."
No. 1 U.S. mobile provider Verizon Wireless, a venture of Verizon Communications (VZ.N) and Vodafone Group Plc (VOD.L), sells Motorola Droid phones and HTC Droid phones.
NPD said that for the first time since it launched in late 2007, Android took the lead from Research In Motion RIM.TO BlackBerry phones in the second quarter, leaving Apple Inc's (AAPL.O) iPhone in third place.
Android had a 33 percent share of the U.S. smartphone market in the quarter while RIM had a 28 percent share and Apple had a 22 percent share, NPD said. (Reporting by Sinead Carew; Editing by Tim Dobbyn)