RUSAL <0486.HK> has rejected an offer to sell its 25 percent stake in Norilsk Nickel to the company, the world's biggest nickel and palladium producer said on Tuesday.

Norilsk Nickel also said that Oleg Deripaska, who controls RUSAL, voted in favor of Norilsk's plan to boost its capitalization, which includes a share buyback.

A source told Reuters that Norilsk Nickel offered to increase its offer for the stake to $14 billion from $12 billion, but RUSAL had asked for $16 billion.

Norilsk Nickel decided not to offer such a high amount, as it was concerned it could harm the company's finances, the source said.

(Reporting by Polina Devitt. Writing by Toni Vorobyova. Editing by Robert MacMillan)