Moscow, Russian Federation — March 21, 2007 — Mobile Telesystems OJSC («MTS» — NYSE: MBT), the largest mobile phone operator in Russia and the CIS, announces the appointment of mr. Marcel stockli as the new Chief Technology Officer (CTO).

Mr. Stockli has more than 10 years of experience in telecommunications. During four years prior to joining MTS, he was Head of Network Planning and Performance Management at Swisscom Mobile AG in Bern, Switzerland, and contributed to the successful launch of EDGE, UMTS and HSDPA.

Mr. Stockli also worked six years at Ericsson Switzerland, where he held a number of key positions and was responsible for managing 3G dimensioning/design and technical sales support of UMTS projects in the country and several West European operators during license bid and initial design phase. Mr. Stockli also has a wealth of experience as a consultant in technical support of 3G implementation and preparation of specialists for network deployment, dimensioning and performance projects.

«Mr. Stockli is a highly qualified professional with significant work experience in the European telecommunications markets and will be of great use for our Company. Marcel?s key objectives will be integrated development of the technical base and IT infrastructure during the 3G network deployment and implementation of new advanced methods for network quality management and latest technological innovations,» commented Sergey Aslanyan, Vice President of MTS for Network and Information Technology.

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Biography

Mr. Marcel Stockliwas born in 1969. Graduated from the Swiss Federal Institute of Technology in Zurich (ETH Zurich). Has more than 10 years experience in the field of telecommunications. Prior to joining MTS from 2002 was Head of Network Planning and Performance Management at Swisscom Mobile AG in Bern, Switzerland. From 1996 to 2002 held a number of key positions at Ericsson AG in Bern, Switzerland.