August 2005

Financial Results for the Second Quarter Ended June 30, 2005

Moscow, Russian Federation — August 30, 2005 — Mobile TeleSystems OJSC (“MTS” — NYSE: MBT), the largest mobile phone operator in Russia and the CIS, today announces excellent financial and operating results for the second quarter of 20051 featuring strong financial performance, robust subscriber growth and ARPU increase.

0788 — Fortune Assistance Center

For the first time, MTS offers its users the Fortune Assistance Center service on 0788.

Health and Beauty Tour!

Do you want to be pampered? Win luxurious prizes with MTS, including a rejuvenating trip for two to the best spa hotel in Baden-Baden!

0834 — “Three Wishes” Tricks for 1 September!

From August 26, 2005 MTS’ Three Wishes voice mail services offers its users a collection of amusing congratulations for the beginning of the school year!

MTS’ New Sales and Customer Care Offices in Sergiev Posad and Orekhovo-Zuevo

MTS is pleased to announce the opening of the new sales and customer care offices in Sergiev Posad and Orekhovo-Zuevo in the Moscow region.

i-mode™ in Russia!

From September 15, 2005, the new revolutionary i-mode service will be available to MTS users!

MTS-Search: Racing Game

Participate in MTS-Search’s Racing Game by sending the message “GO” to 7788 for the chance to win an outboard motorboat or other prize!

Second 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 Second Quarter 2005 Financial and Operating Results on Tuesday, August 30, 2005.

MTS Services at the Samsung Gallery

The First Mobile Exposition in Russia Being Held by MTS in Conjunction with Samsung Electronics

0633 — Echo Moskvy Express-Information!

MTS offers its users a unique opportunity to ask questions using the call-center specialists on Echo Moskvy’s radio broadcast via its quick dial 0633 Express-Information service.

0847 — Send Congratulations and Play Tricks for 1 September!

Send an original congratulation recorded by the voices of well-known politicians to your friends for the beginning of the school year.

0930 — Voice Dating Service

MTS’ Single Information Service on 0930 offers users a new voice dating service.

MTS Announces Subscriber Growth Numbers for July 2005

Moscow, Russian Federation — August 10, 2005 — Mobile TeleSystems OJSC (“MTS” — NYSE: MBT), the largest mobile phone operator in Russia and the CIS, announces that its consolidated subscriber base reached 46.37 million users on July 31, 2005.

Contact investor relations:

+ 7 495 223 20 25

MTS Investor Relations
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