Moscow, Russian Federation – March 19, 2004 – Mobile TeleSystems OJSC (“MTS” - NYSE: MBT), the largest mobile phone operator in Russia and Ukraine, announces that it has acquired an additional 11% of Siberian Cellular Systems-900 (SCS-900). As a result of this transaction, MTS now owns 99.5% of the company.

In line with its strategy to consolidate ownership in its subsidiaries, MTS has acquired an additional 11% stake in SCS-900 from a private company for $8.5 million, increasing its ownership to 99.5%.

SCS-900 is a leading mobile operator in the Novosibirsk region (population 2.7 million) and the Altai Republic (population 202,000), providing services to approximately 512,800 subscribers. SCS-900 operates under the MTS brand and offers the complete range of MTS’ national products.

SCS-900’s net revenue for the first nine months of 2003 was $47.7 million, its operating income was $23.0 [1] million and net income was $16.6 million. ARPU for the same period was at $14.6. SCS-900’s net debt as of September 30, 2003 was approximately $2.4 million.

According to the independent market research agency, AC&M-Consulting, mobile penetration in the Novosibirsk region was at 27.3% and SCS-900’s market share was approximately 60% as of December 31, 2003.

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For further information, contact:

Mobile TeleSystems, Moscow

Investor and Public Relations                                                                        tel: +7 095 911 6553

Andrey Braginski                                                                                    e-mail: ir@mts.ru

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Mobile TeleSystems OJSC (“MTS”) is the largest mobile phone operator in Russia and Ukraine. Together with its subsidiaries, the company services over 18.25 million subscribers. The regions of Russia, as well as Belarus and Ukraine, in which MTS and its subsidiaries are licensed to provide GSM services, have a total population of approximately 200.6 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. 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.