SEATTLE (Bloomberg) - Microsoft Corp.'s effort to gain ground on Google Inc. with its new Bing search engine got a boost yesterday from data showing an increase in its share of US search results, according to ComScore Inc.

Microsoft's share rose to 11.1 percent in the June 2 - 6 period, Bing's first week in operation, from 9.1 percent a week prior, ComScore said on its website. Average daily penetration among searchers, a measure of how many people are being reached by the product, rose to 15.5 percent from 13.8 percent.

Bing debuted on May 28 and Microsoft released it the following week, bolstered by an extensive television and Internet advertising campaign. Bing represents an overhaul of the Redmond, Washington-based company's search product after more than five years of investment resulted in share losses to industry leader Google.

The data "showed a substantial improvement in Microsoft's position in the search market in the days following Bing's introduction," Reston, Virginia-based ComScore said.

Adam Sohn, a director in Microsoft's Online Services Business, declined to comment on the share data. Google, in an e-mail, reiterated its statement that it "welcomes competition that helps deliver useful information to users". Kim Rubey, a spokeswoman for Yahoo! Inc., operator of the No.2 US search engine, was not immediately available to comment.

Microsoft, the world's largest software maker, rose two cents to $22.07 at 1.44 p.m. New York time on the Nasdaq Stock Market. The shares had gained 13 percent this year before yesterday. Google fell $2.52 to $436.25, and Yahoo rose eight cents to $16.27.

Even though Bing has only been out for a week, it is already performing better than past Microsoft efforts to improve and market its search engine, said Greg Sterling, principal at consulting and research firm Sterling Market Intelligence in San Francisco.

"People are trying it out and some number of people seem to be more than just lookie loos," said Mr. Sterling, who is also a contributor to the Search Engine Land Website. "In the case of a launch like this, you often get a spike on the first day and then it goes away, but there does seem to be some usage ongoing here."

ComScore's most recent monthly data shows Google with an eight-to-one lead over Microsoft in US search share. Microsoft focused on attracting users to Bing by enhancing how results are categorised and by exploiting specific niches like travel and shopping. It's being marketed as a "decision engine", that helps customers find the right information more quickly.

"The ultimate performance of Bing depends on the extent to which it generates more trial through its extensive launch campaign and whether it retains those trial users," Mike Hurt, ComScore's senior vice president, said in a statement. "It appears it is off to a good start."

Microsoft's search engine will not catch Google any time soon, Mr. Sterling said.

Still, "Bing could catch on with a sizeable minority of users", he said. "Yahoo is the engine that is vulnerable here. They seem to be coasting a little bit."