Saudi grants approval for UBS securities business

* UBS Saudi Arabia to offer full range of services

* Part of expansion in Middle East

ZURICH, July 14 (Reuters) - Saudi authorities have granted approval for UBS (UBS.N) (UBSN.VX) to start securities business activities, which the Swiss bank said on Tuesday would help it expand in the fast-growing Middle Eastern region.

In establishing the business, UBS said it had partnerned with Mohammed Al Dhoheyan, former chief executive of the Saudi Development and Management House for Investments, and MerchantBridge, an equity house investing in the Middle East.

UBS, the world's second largest wealth manager by private client assets, is struggling to rebuild its once powerful brand after massive investments into risky U.S. assets forced it to make more writedowns than any other European bank.

Last year, UBS won won a licence to open an investment banking branch in Saudi Arabia, the world's top oil exporter and the region's largest economy, joining a growing list of western banks boosting their presence in the booming Gulf Arab region. (Reporting by Emma Thomasson; Editing by Dan Lalor)