UC Rusal, the world's biggest aluminium producer, is taking 25 per cent of Norilsk Nickel in what could be the first step towards the creation of a Russian metals and mining group on the scale of Rio Tinto or BHP Billiton.

The deal could eventually lead to a full tie-up of a group that produces 12 per cent of the world's aluminium and the world's biggest producer of nickel and palladium.