Moscow, Russian Federation – Mobile TeleSystems OJSC (“MTS” – NYSE: MBT), the largest mobile phone operator in Russia and the CIS, announces that Moody's Investors Service has confirmed the Ba2 corporate family and senior unsecured rating of MTS following the completion of MTS’ acquisition of a controlling stake in Comstar-UTS. Moody's also reiterated that the outlook on the rating remains stable.