Microsoft's chief executive vowed to "kill Google" in an expletive-laden tirade against the firm, according to US court documents filed by Google.

The claim was made in a sworn statement by Mark Lucovsky, a former Microsoft employee who quit for Google in 2004.

Microsoft chief Steve Ballmer has denied the claims, saying they are a "gross exaggeration of what actually took place".

The statement is the latest salvo in a bitter legal battle between the firms.

In his sworn statement, Mr Lucovsky - a key Windows architect - alleged that Mr Ballmer hurled a chair across the room when he informed him he was moving to Google, before launching into an abusive tirade against Google's chief executive Eric Schmidt.

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