Three private equity firms have agreed to buy a combined about 10 percent stake of a flagship unit of China UnionPay, as the country's monopoly card payments service provider aims to go public next year, sources with direct knowledge of the deal said on Friday.

CITIC Private Equity, an investment arm of China's top brokerage CITIC Securities (600030.SS) and V-Stone Investments, the private equity arm of Chinese men's fashion maker Youngor Group, are among the buyers for China UnionPay Merchants Service Co Ltd, said the sources.

The third buyer is a local investor and they have agreed to pay about 800 million yuan ($117.1 million) for a total of 10 percent of the China UnionPay unit, said the sources.

 ($1=6.830 Yuan)

 (Reporting by George Chen; Editing by Jacqueline Wong)