Google's Seoul offices was raided by South Korean officials as part of an ongoing antitrust probe into the Internet giant's Android tactics.
The Korean Fair Trade Commission, which ordered the raid, is investigating Google after South Korean search companies complained the Mountain View, Calif.-based company's Android OS stifles mobile search competition.
In April, NHN and Daum complained Google uses monopolistic tactics to force Android phones to use its search and navigation tool. Google denied those charges and said it will work with South Korean officials to address any questions.
NHN claims Google banned South Korean phone makers from including rival Web search apps by delaying handset certification for manufacturers that wouldn't agree to its conditions.
Meanwhile, Daum alleged Google interfered when it tried to install its search engine on phones.
Google maintains handset makers are free to decide what service to include on their devices, since Android is an open platform.
Android is particularly popular among South Korean smartphone makers, with about 70 percent of its more than 10 million smartphones using the OS, according to Hanwha Securities.
"Using Google is a choice -- and there are lots of other choices available to users for getting information," Amti Singhal, a Google fellow, wrote on the company's blog.
Google faces global scrutiny in countries beyond South Korea as its Android system gains steam worldwide.
The U.S. Federal Trade Commission is inquiring whether Google prevents smartphone makers from using competitors' services. Authorities are investigating if Google ranks its own products, such as "Places" listings and Google Finance products, above rival services in search results.
Google says Android doesn't block other search engines. However, Fairsearch.org, which represents rival search engines Microsoft, Expedia and Sabre Holdings, says Google is long overdue for an antitrust investigation.
Antitrust complaints may continue against Google as it strengthens its position with the Android OS, which continues to flourish. Customers activate more than 500,000 Android-based smartphones every day, and as those numbers continue to grow, more search engine companies may increasingly allege Google uses unfair practices to quash competition.
