MOSCOW, Feb 16 (Reuters) – Russian billionaire Vladimir Potanin has made an offer to purchase a minority stake in Russia’s Norilsk Nickel from Roman Abramovich and his partners, Interros holding, which manages Potanin’s assets, told Reuters. Aluminium giant Rusal, which also owns a stake in Nornickel, is seeking an injunction in a London court to block the deal, Interros said. Rusal and a representative of Abramovich declined to comment.