Moscow, Russian Federation — August 14, 2003 — Mobile TeleSystems OJSC (“MTS” — NYSE: MBT), the largest mobile phone operator in Russia in terms of subscribers, today completed a previously announced transaction to acquire an additional 46.65% stake in Uraltel, the largest mobile phone operator in the Sverdlovsk region of Russia.

As previously announced, MTS has agreed to acquire, in a series of related transactions, equity interests in five regional mobile phone companies for a total of $71 million. In accordance with this agreement, MTS has completed the purchase of a 43.7% additional stake in Uraltel from MCT Corp, a Delaware corporation. MTS has also acquired another 2.95% of Uraltel from a shareholder unrelated to MCT Corp.

MTS previously held a 53.2% stake in Uraltel through its 100%-owned subsidiary, Telecom-900. The transaction takes Telecom-900 ownership in Uraltel to 99.85%.

Uraltel is the largest cellular operator in the Sverdlovsk region of the Urals, which has a population of 4.5 million. The Company provided services to approximately 244,000 subscribers as of June 30, 2003. Average monthly revenue per user (ARPU) for the first six months of 2003 was $20.

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Mobile TeleSystems OJSC (or “MTS”) is the largest mobile phone operator in Russia and Eastern Europe in terms of the number of subscribers. Together with its subsidiaries, the Company services over 12.8 million subscribers. MTS and its subsidiaries are licensed to provide GSM services in 61 regions of Russia, in the Ukraine and in Belarus, which together have a total population of approximately 172.7 million. Since June 2000, MTS’ shares have been listed on the New York Stock Exchange with the ticker symbol MBT. Additional information about MTS can be found on MTS’ website at www.mtsgsm.com.

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Some of the information in this press release may contain projections or other forward-looking statements regarding future events or the future financial performance of MTS, as defined in the safe harbor provisions of the U. S. Private Securities Litigation Reform Act of 1995. You can identify forward looking statements by terms such as “expect,” “believe,” “anticipate,” “estimate,” “intend,” “will,” “could,” “may” or “might” the negative of such terms or other similar expressions. We wish to caution you that these statements are only predictions and that actual events or results may differ materially. We do not intend to update these statements to reflect events and circumstances occurring after the date hereof or to reflect the occurrence of unanticipated events. We refer you to the documents MTS files from time to time with the U. S. Securities and Exchange Commission, specifically, the Company’s most recent Form 20-F, as amended. These documents contain and identify important factors, including those contained in the section captioned “Risk Factors,” that could cause the actual results to differ materially from those contained in our projections or forward-looking statements, including, among others, potential fluctuations in quarterly results, our competitive environment, dependence on new service development and tariff structures; rapid technological and market change, acquisition strategy, risks associated with telecommunications infrastructure, risks associated with operating in Russia, volatility of stock price, financial risk management, and future growth subject to risks.

For further information contact:

Mobile TeleSystems, Moscow
Andrey Braginski, Investor and Public Relations
tel: +7 (095) 911-65-53e-mail: ir@mts.ru