Experian Hitwise on Tuesday reported that Bing and Yahoo! online search engines lost ground in the United States in September while Google inched ahead slightly.
Google handled 71.08 percent of all US Internet searches in the four weeks ending October 3, while Yahoo! and Bing accounted for 16.38 percent and 8.96 percent respectively, according to Hitwise.
Ask.com was the biggest winner, with its share of US searches climbing 8 percent to 2.56 percent in September as compared with August.
Microsoft's Bing saw its share of the US online search market dip 5 percent in the month-to-month comparison, while the number of searches at Yahoo! was down 3 percent, Hitwise reported.
Google last week rolled out search engine refinements as Microsoft continues an aggressive campaign to lure people to Bing.
The Internet giant's modifications include tools that let people limit online searches to only serve up results from the past hour, or by specific date ranges.
Google users can choose to be shown search only results from blogs, news, or Web pages that they have visited or those they haven't visited.
The Bing search engine Microsoft launched in May was designed to intuitively understand what people are seeking on the Internet and challenge online king Google.
The US software colossus described Bing as a "Decision Engine" aimed at online shoppers trying to make buying decisions, plan trips, research health matters or find local businesses.
Bing posted a slight increase in its share of the US search market in August, a third month in a row of modest gains, according to online tracking firm comScore.
Yahoo! and Microsoft, after months of negotiations, unveiled a 10-year Web search and advertising partnership in late July that set the stage for a joint offensive against Google.
Under the agreement, Yahoo! will use Microsoft's search engine on its own sites while Yahoo! will provide the exclusive global sales force for premium advertisers.
Microsoft is integrating messages from prominent users of wildly popular micro-blogging service Twitter into results generated by Bing.Reuse content