In a violent outburst, Microsoft CEO Steve Ballmer vowed to "kill Google" last November, a court report claims.

Though Ballmer dismisses the event as a "gross exaggeration", the allegations are contained in a sworn statement provided to the courts as part of Microsoft's attempt to prosecute Google for hiring away senior Microsoft executive Kai Fu-Lee in July. Fu-Lee is to run Google's Chinese research centre.

Associated Press reports the event as described in a sworn declaration by a former Microsoft engineer, Mark Lucovsky, who also quit Microsoft to move to Google.

After learning Lucovsky was leaving to work at Google, "Ballmer picked up his chair and hurled it across his office," the report claims.

Ballmer then pejoratively berated Google CEO Eric Schmidt, Lucovsky recalled.

“I'm going to f------ bury that guy. I have done it before, and I will do it again,” the declaration quotes Ballmer as saying. “I'm going to f------ kill Google.”

Microsoft is accusing Fu-Lee of breach of contract.