Moscow, Russian Federation – Mobile TeleSystems OJSC (“MTS” - NYSE: MBT), the largest mobile phone operator in Russia and the CIS, announces that Standard & Poor's Ratings Services has upgraded the long-term corporate credit rating of MTS to “BB” from “BB-“. The outlook on the ratings remains positive.

In a press release circulated today, S&P cites as reason for the upgrade: “the company's strong business characteristics, based on solid positions in the Russian and Ukrainian mobile markets. These characteristics include robust growth with steadily improving economies of scale; sound operating profitability; strong cash flows; and declining financial risk.”

Please refer to www.sandp.ru for additional information.