Ad Hoc Notice
Moscow, Russian Federation – Mobile TeleSystems OJSC (“MTS” – NYSE: MBT), the leading telecommunications operator in Russia and the CIS, announces that Standard & Poor's Ratings Services raised its long-term foreign and local currency corporate credit rating to 'BBB-' from 'BB+'. The outlook on the foreign currency rating is negative and that on the local currency rating is stable. Ratings on the Company's senior unsecured debt were raised to 'BBB-' from 'BB+'. This represents a one-notch upgrade and classifies MTS as investment grade.