Davis Polk & Wardwell is in the thick of battle for control of a Russian cellphone operator that is pitting one of the country’s oligarchs against the firm’s client, a leading Swedish telecommunications company.

Stockholm-based Tele2 AB announced this week that it plans to sell its Tele2 Russia cellphone unit to Russian financial services giant VTB Bank for $3.5 billion, including debt. For its part, state-owned VTB confirmed Thursday that the transaction would proceed, with first deputy president and chairman of the management board Yury Solovev proclaiming that the “legally binding” agreement with Tele2 was complete.