DBS Group Holdings, Southeast Asia’s biggest bank, said it will take over Royal Bank of Scotland Group Plc.’s retail and commercial banking businesses in China.

RBS will transfer close to 25,000 clients in Shanghai, Beijing and Shenzhen to DBS China, Singapore-based DBS said in a statement on its website today. No amount was disclosed for the transaction, which is expected to be completed within six months.

DBS Chief Executive Officer Piyush Gupta, seeking to lift a stock that’s trailed rivals in 2010, said last month he plans to improve return on equity by building businesses that cater to wealthy individuals and small companies, and by expanding in China, India and Indonesia. For RBS, the deal is part of asset disposals following a government bailout and record losses.

Singapore-based DBS aims to generate about 40% of revenue from the city state in five years, down from about two-thirds now, according to a plan unveiled in February. Greater China would make up 30%, DBS has said. South Asia and the rest of Southeast Asia may contribute another 30%.

China opened its banking industry to overseas companies in December 2006, sparking a rush among foreign lenders to compete for the nation’s corporate and household savings, which reached $8 trillion ($10.5 trillion) in September. The country’s loan growth averaged 20% from 2005 to 2009, according to the central bank.