Under a drastic shrinking of its investment banking operations, RBS said last month it will pull out of 25 countries, while substantially cutting its presence in Asia and the United States within its corporate and institutional banking business.

The bank was considering selling or winding down operations in the Czech Republic, Russia, the Middle East and Africa, Kazakhstan, Turkey and Poland, a source familiar with the matter told Reuters. The bank will exit Romania and Slovakia, the source said.

The bank's spokeswoman declined to comment on the specific countries involved.

The lender, 79-percent owned by the British government, is under pressure to scale down its international business and sharpen its focus on its domestic market after receiving 45.5 billion pounds ($67.2 billion) in government assistance during the financial crisis of 2007-9.

RBS's credit exposure to the CEEMEA region, as well as central Asia and institutions such as the World Bank, was 19.1 billion pounds in 2013, representing 3.4 percent of its 573 billion pounds of credit risk assets, according to its annual report for that year. It had 1.7 billion pounds of exposure to CEEMEA's oil and gas industry at the end of 2014, its 2014 annual results show.

In the Middle East and Africa -- where it has offices in the United Arab Emirates, Qatar and South Africa -- it is gauging interest for the sale of its corporate debt and debt capital markets business, but will wind down the operations if buyers are not found, the source said.

The bank will honour legal obligations relating to existing customers and was in close talks with the affected customers about what would happen with their business in the future, said the source.

(Reporting by Tom Arnold; Editing by Andrew Torchia and Louise Heavens)

By Tom Arnold