The Internet search world was rocked by a rare spell of intrigue and acrimony on Tuesday, as Google, the world’s No. 1 search company accused rival Microsoft of copying its search results, leading to a public slap-fight between the two tech giants.

“This is the first time in my 20-year career that I am seeing such unethical behavior in another company,” Google Fellow Amit Singhal declared in an interview with Reuters on Tuesday, following an earlier blog post in which he accused Microsoft of providing “recycled search results.”

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Microsoft was quick to return fire, insisting it did not copy Google’s search results and describing Google as engaging in everything from “creative tactics” to click fraud. Microsoft PR honcho Frank Shaw unleashed a fusillade of Tweets throughout the day, stating in one of them that Google was seeking to change the subject because the company was under investigation in the U.S. and Europe for manipulating search results.

The brouhaha started after the tech blog SearchEngineLand ran a story about a sting operation that Google engineers conducted in December to prove suspicions about Microsoft copying its search results. In the “scientific experiment,” Singhal said that Google tweaked its search engine so that searches for certain gibberish phrases returned specific results – for example a search on Google for the nonsensical term “hiybbprqag” would deliver a link to the Wiltern arena in Los Angeles as a top result.

Google then had about 20 of its engineers perform Google searches for the fake terms on laptops equipped with the Microsoft Internet Explorer browser and a Bing toolbar. Sure enough, says Singhal, within a couple of weeks, a search for “hiybbprqag” on Microsoft’s Bing search engine also returned a link to the Wiltern arena.