Google Inc has bought online advertising technology company AdMeld for $400 million, according to an influential technology blog.

The deal, which was reported by TechCrunch citing multiple unnamed sources, would mark Google's latest effort to bolster its business in the market for graphical, display ads, where it competes with rivals including Yahoo Inc and Facebook.

Four-year-old AdMeld counts Discovery Communications, FOX News, Hearst Television, and The Weather Channel among its clients, according to its website.

It has raised $30 million in funding from investors including the Foundry Group, Spark Capital, Norwest Venture Partners and Time Warner Investments, TechCrunch cited multiple unidentified sources as saying.

Google, the world's No. 1 Internet search engine, declined to comment.

Google has been on an acquisition spree, spending $1.8 billion on more than 40 companies in 2010.

The vast majority of Google's revenue, which totaled roughly $29 billion in 2010, comes from small ads that appear alongside its search results. But the company has stepped up efforts to tap into the display advertising market.

In October, Google said its display advertising business was generating revenue at an annualized run rate of $2.5 billion.

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