May 2005

31.05.2005
MTS Announces the Launch of its Network in the Republic of Tyva

The Republic of Tyva is the 79th Russian region to receive MTS’ network coverage.

31.05.2005
MTS’ Intranet Roaming Zone: the Republic of Tyva

From May 31, 2005 the Republic of Tyva will be integrated into MTS’ intranet roaming zone.

24.05.2005
First Quarter 2005 Financial Results Announcement and Conference Call

The management of Mobile TeleSystems (MTS) will be holding a conference call to discuss the Company’s First Quarter 2005 Financial and Operating Results on Wednesday, June 01, 2005.

19.05.2005
MTS Announces Recommended Amount of Dividends

Moscow, Russia — May 19, 2005 — Mobile TeleSystems OJSC (“MTS” — NYSE: MBT), the largest mobile phone operator in Russia and the CIS, announces the recommended amount of dividends.

17.05.2005
MTS’ Intranet Roaming Zone: the Republic of Kalmykia

From May 17, 2005, the Republic of Kalmykia will be integrated into MTS’ intranet roaming zone.

17.05.2005
MTS Announces the Launch of its Network in the Republic of Kalmykia

The Republic of Kalmykia is the 78th Russian region to receive MTS’ network coverage.

13.05.2005
MTS to be Included in the MSCI EM Index

Mobile TeleSystems OJSC reports that the Company’s ADRs will be added to the Morgan Stanley Capital International Emerging Markets (MSCI EM) Index, effective May 31, 2005.

06.05.2005
MTS Announces Subscriber Growth Numbers for April 2005

Moscow, Russia — May 06, 2005 — Mobile TeleSystems OJSC (“MTS” — NYSE: MBT), the largest mobile phone operator in Russia and the CIS, announces that its consolidated subscriber base reached 40.63 million users on April 30, 2005.

04.05.2005
MTS and Research In Motion to Offer BlackBerry in Russia

Moscow, Russia and Waterloo, Canada — May 4, 2005 — Mobile TeleSystems OJSC (“MTS” — NYSE: MBT), the largest mobile phone operator in Russia and the CIS and Research In Motion (RIM) (Nasdaq: RIMM; TSX: RIM) today announced plans to offer BlackBerry®, a leading wireless platform, to mobile customers in Russia.

Contact investor relations:

+ 7 495 223 20 25 ir@mts.ru

MTS Investor Relations
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