Moscow, Russian Federation — September 5, 2003 — Mobile TeleSystems OJSC (“MTS” — NYSE: MBT), the largest mobile phone operator in Russia in terms of subscribers, today announces a transaction to acquire Tomsk Cellular Communications. The completion of this deal will make MTS the leader in the cellular market of the Siberian macro region of Russia.

MTS has signed an agreement to acquire 100% in Tomsk Cellular Communications for $47 million. Tomsk Cellular Communications is the leading cellular operator in the Tomsk region of the Siberian macro region. The company holds licenses to provide GSM 900/1800 mobile cellular communications in the Tomsk region. The company’s subscriber base as of August 31, 2003 stood at 183,000. The network has been operational since August 1999. Currently, Tomsk Cellular Communications’ network covers 70% of the region’s population. The company’s net debt at the acquisition is approximately $1.0 million.

The region’s population is 1.05 million. According to AC&M-Consulting, the penetration in the Tomsk region exceeds 22%, and the company’s market share stands at 80%.

After the completion of this acquisition, MTS will become the leader in the cellular market of the Siberian macro region of Russia in terms of subscribers.

Completion of the transaction is subject to a number of conditions. No assurance can be given that the transaction will be completed on the terms and conditions described, or at all.

* * *

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.

* * *

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