Norilsk Nickel's board approved the sale of up to $7bn in energy assets yesterday and agreed to consider a share buyback in a move that could signal growing resistance to takeover attempts by UC Rusal.

Oleg Deripaska's Rusal has agreed to buy a 29 percent stake in Norilsk from Mikhail Prokhorov, the billionaire former co-owner of the mining group, in a deal seen by Rusal as the first step toward a full takeover.