Moscow– June 16, 2003 – Mobile TeleSystems OJSC (“MTS” - NYSE: MBT), the largest mobile phone operator in Russia and Central and Eastern Europe[1] today announces that it has increased its ownership in Ukrainian Mobile Communications (UMC) to 83.7% through the acquisition of an additional 26% stake in the company.

MTS has completed the acquisition of a 26% stake in UMC pursuant to the terms and conditions of the call option agreement with Ukrtelecom signed on November 5, 2002.  As the result of the transaction, MTS’ ownership in UMC has increased from 57.7% to 83.7%.  MTS has paid $87.57 million for the stake and the funds have been transferred to Ukrtelecom in full.

As previously announced, MTS acquired a 57.7% stake in UMC, one of the two leading mobile operators in Ukraine providing services to over 1.9 million subscribers as of beginning of June 2003.  MTS purchased the stake for $194.2 million from KPN (16.3%), Deutsche Telekom (16.3%) and Ukrtelecom (25%) and entered into option agreements with Ukrtelecom and TDC to purchase their respective 26% and 16.3% stakes in the company.  If MTS chooses to exercise the option agreement with TDC, the Company's will own a 100% stake in UMC.

MTS consolidates UMC into its financial and operating results as of March 1, 2003.

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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.

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Mobile TeleSystems OJSC (or "MTS") is the largest mobile phone operator in Russia, and Central and Eastern Europe. Together with its subsidiaries, the company services over 11 million subscribers. The 58 regions of Russia as well as in Belarus and Ukraine in which MTS and its subsidiaries are licensed to provide GSM services have a total population of approximately 169.2 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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For further information contact:

Mobile TeleSystems, Moscow

Investor and Public Relations                                                            tel: +7095 911 6553

Andrey Braginski                                                                        e-mail: ir@mts.ru

Press Secretary                                                                                    tel.: +7095 737 4530

Eva Prokofieva                                                                                  e-mail: evp@mts.ru

Gavin Anderson & Company, London

Halldor Larusson                                                    tel: +44 (0) 20 7554 1400