Microsoft's new Internet search engine Bing posted a modest gain in its share of the US search market in December while partner Yahoo! saw its share dip slightly, online tracking firm comScore said.
Google remained the overwhelming leader of the lucrative US search and advertising market last month, increasing its share to 65.7 percent from 65.6 percent in November, according to comScore figures released Friday.
Yahoo! saw its share of the search market fall to 17.3 percent in December from 17.5 percent the previous month, comScore said, while Bing's share rose to 10.7 percent from 10.3 percent.
Ask.com's share fell to 3.7 percent from 3.8 percent while AOL's dropped to 2.6 percent from 2.8 percent.
December was the seventh month in a row of modest gains in search share for Bing, which Microsoft unveiled in June accompanied by a 100-million-dollar advertising campaign in a bid to challenge search juggernaut Google.
Microsoft and Google have been consistently upgrading online search service features in what has thus far been a lopsided duel favouring the Mountain View, California-based Internet king over the software giant.
The competitors have been focused on improving mobile search offerings and incorporating real-time content from popular online communities such as Twitter and Facebook into search results.
Microsoft chief executive Steve Ballmer announced last week at the Consumer Electronics Show in Las Vegas that Bing would be the default search engine on Hewlett-Packard computers in 42 countries.
Yahoo! and Microsoft unveiled a 10-year Web search and advertising partnership in 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 providing the exclusive global sales force for premium advertisers.
Explore further: When a selfie is not enough: India abuzz over 'velfie' craze