Russia's Alfa Telecom offered $2.8 billion on Tuesday to buy back a 13.76 percent stake of Turkcell , a deal that would double its holding in Turkey's top mobile operator after a seven-year battle for control of the company. Alfa Telecom said in a statement it had offered $54.9 million per share for 51 of Turkcell's class-B shares, which are being held with Turkey's state-run Ziraat Bank [TCZIR.UL] as collateral for a loan.