Vodafone Group PLC (VOD.LN), the world's biggest mobile operator by revenue, Thursday moved to strengthen its beleaguered operations in Europe by appointing two chiefs to oversee its biggest market.

Nearly two months after losing its European chief executive, Michel Combes, to French telecom and media company Vivendi SA's (VIV.FR) mobile unit SFR, Vodafone had decided to split the role in Europe into two new operating regions, Northern & Central Europe and Southern Europe.

Philipp Humm--who resigned 24 hours earlier as CEO of T-Mobile USA, a unit of Germany's Deutsche Telekom AG (DTE.XE)-- has been appointed CEO of Vodafone's Northern & Central Europe business, overseeing operations in Germany, the U.K., the Netherlands, Turkey, Ireland, Hungary, the Czech Republic and Romania.

Vodafone's CEO in Italy, Paolo Bertoluzzo, has been given additional responsibility as CEO of the mobile operator's Southern Europe operations, which includes Italy, Spain, Portugal, Greece, Albania and Malta.

Chief Executive Vittorio Colao said in a statement that the new regional structure "will underpin our strategy focused on meeting our customers' long-term needs", and that both men will be "strong additions" to the Vodafone Group Executive Committee.

Mr Humm will start in his new role on Oct. 1, and Mr Bertoluzzo's position is effective from Aug. 1.

Vodafone last month booked a 13% fall in annual net profit to 6.96 billion pounds ($10.82 billion) as dismal economic conditions in Spain, Italy, Greece and Portugal hit customer spending there, prompting a GBP4 billion impairment charge. The U.K.-based operator also warned at the time that conditions in Europe are likely to remain grim for the rest of the year.

Write to Lilly Vitorovich at lilly.vitorovich@dowjones.com; Twitter: @LillyVitorovich