Google continued to bolster its hold on the US search market in August when it captured 63 percent of 11 billion searches, according to data released Thursday.

The share of searches on Google sites increased from 61 percent in July, according to ComScore, which measures and analyzes online activity. In August, Google was followed by Yahoo (which captured a 19 percent share of searches), Microsoft (8 percent share), AOL (4.3 percent) and the Ask Network (4 percent).

ComScore said that of the 11 billion searches on core sites by Americans in August, Google handled 7 billion (up 2 percent from July), Yahoo 2 billion and Microsoft 977 million.

Google's slight increase in August came at the expense of Yahoo and Microsoft, which trended downwards by 0.9 percent and 0.6 percent respectively, the report said.

ComScore also tracked the top overall Web properties - which includes the sites of search companies and their subsidiaries. Google-owned sites, which include video sharing site YouTube, led that list with 10 billion searches, a 2 percent increase over July. Yahoo Sites, which include photo sharing site Flickr, ranked second with 2 billion while Microsoft sites followed with 1 billion and AOL and its Mapquest site had 839 million searches.

Google's continued domination of the search market comes in the midst of its effort to defend its proposed search advertising deal with Yahoo. The plan, which would have Yahoo running Google ads alongside its search results, has come under fire from advertising groups while the US Department of Justice hired a top litigator to consider if the deal violates antitrust regulations.