Magnus Carlsen, the reigning king of chess, has called on Microsoft for help as fears grow Russian hackers will target him before next week's World Championship.

The man dubbed the "Mozart of chess" has spent months using high-powered chess computers to meticulously prepare moves for his gruelling 12-game match against challenger Sergey Karjakin.

But any leak of his analysis would hand a significant advantage to Crimean-born Karjakin, the fiercely-patriotic darling of Russian president Vladimir Putin.