Yahoo is testing blog-search technology in Korea - likely an indication of what's to come in the next few weeks in the U.S. market - in a move that will challenge current niche leader Technorati, reports CNET. Yahoo has introduced the search technology on its Korean blog site, with search tools that let visitors retrieve content and photos from all blogs, those with recent postings, or pages that users have marked as their favorites.

Search tools would help users find not only blog content but also the advertising that is appearing alongside that content more and more. Yesterday, Yahoo introduced an advertising network for small publishers, including blogs.

Yahoo rivals Google and MSN do not have blog search tools, although Google oes include some blogs in its search results. Meanwhile, the amount of blog content is expanding rapidly. Technorati this week reported that the number of blogs is doubling every five and a half months.

Blog search would also complement Yahoo's social-networking and blog-publishing service, Yahoo 360, launched in March and still in beta.