Microsoft has vowed to hunt down the pirates responsible for distributing illegally obtained copies of its hotly anticipated Halo 2 game onto the internet.

The leak, just three weeks before the Xbox game is due to hit the shelves, has seen the illicit code turn up on a variety of piracy websites and newsgroups.

Microsoft issued a statement saying that it is "aggressively pursuing the source of this illegal act".

The software giant claimed that official orders for Halo 2 have eclipsed the 1.5 million mark in the US.

It added that the game is "poised to generate more revenue in 24 hours than day-one sales of any full feature movie in entertainment history, including Spider-man 2, Harry Potter and the Prisoner of Azkaban and Matrix: Reloaded".

The first copy of Halo 2 will be distributed at midnight in the largest Toys R Us in the world located in Times Square, New York on 9 November.