April 30, 2003, Moscow, Russia. Mobile TeleSystems (MTS – NYSE: MBT), the largest mobile phone operator in Russia as well as in Eastern and Central Europe1, announced the decision to exercise its option right for acquiring an additional 26% stake in the company Ukrainian Mobile Communication (UMC).On April 28, 2003 MTS informed UkrTelecom JSC of the intention to exercise its option right for acquiring a 26% stake in UMC in accordance with the agreement on option deal for the call signed on November 5, 2002. Under this agreement this stake costs $87.57 million. It is expected that the deal will be completed no later than in mid-June 2003. In case the deal is done, MTS’ stake in UMC will increase from 57.7% to 83.7%.

As was reported earlier, MTS acquired a 57.7% stake in UMC, one of the two leading mobile phone operators of Ukraine servicing over 1.8 million subscribers. It bought this stake for $194.2 million from the companies KPN (16.3%), Deutsche Telekom (16.3%) and Ukrtelecom JSC (25%). MTS also signed option agreements with the companies TDC and Ukrtelecom JSC on acquiring their stakes in UMC (16.3% and 26% accordingly). In case all these option rights are executed, MTS’ stake in UMC will equal 100%.MTS has been including UMC’ indexes in its financial and operating accounting since March 1, 2003.

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Completing the deal depends on implementation of some provisions by both sides and receiving of necessary mutual concessions on several points in accordance with the option call agreement. Any considerable delay with obtaining satisfactory concessions or unfavorable terms that they might contain could have a negative impact on MTS’ business, financial status of results of its activity. All these might result in its refusal to acquire that stake and there could be no guarantees that such an additional sale of shares will take place.Some of the statements in this press release may contain projections or other forecasts regarding future events of the future financial performance of the Company, as defined in provisions of the U.S. Private Securities Litigation Act of 1995. Such statements contain terms “as expected”, “estimate”, "intend", "will", "might be" or other similar terms. We wish to caution You that these statements are only predictions and that actual events or results may differ. We do not intend to update these statements to reflect events and actual results. We refer you to the documents that the Company files from time to time with the U.S. Securities and Exchange Commission, including Form 20-F. These documents contain and identify important factors including those mentioned in the Form 20-F section captioned “Risk Factors”. These factors may cause the actual results to differ from projections and forecasts. They include: 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 connected with operating in the Russian market, volatility of stock price, financial management risk and emergence of other risk factors.

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Mobile TeleSystems JSC is the largest operator of the mobile communication in Russia as well as in Eastern and Central Europe. Together with its subsidiaries MTS provides GSM mobile communication services for over 9.8 million subscribers in Russia, as well as in Belarus and Ukraine. The Company and its subsidiaries are licensed to cover the territory that has a total population of about 169.2 million people. Since 2000, MTS’ shares have been listed on the New York Stock Exchange (NYSE) with the ticker symbol MBT. Additional information about the Company can be found on its website at www.mts.ru.

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For additional information, please, contact:

Mobile TeleSystems JSC
Andrei Braginsky,

Director,

Investor and Public Relations

Phone: +7 (095) 911 6553
E-mail: ir@mts.ru

Eva Prokofieva
Press Secretary
Phone: +7 (095) 737 4530
E-mail: eva@mts.ru