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HANOI/HONG KONG, April 12 (Reuters) - CVC Capital Partners has exited Vietnam's fourth-biggest private commercial lender, Asia Commercial Bank (ACB), after its investment unit disposed of its remaining 4.99% stake for around $220 million, three people with knowledge of the matter said.

The Europe-based alternative investment firm had disposed of the remaining stake via a unit called Sather Gate, the three people said. The buyer is a U.S.-based institutional investor, according to two of the people.

The people declined to be named as the matter was private. CVC and ACB did not immediately respond to Reuters requests seeking comment on Friday.

The exit followed a stake sale in early April by another investment vehicle of CVC, called Whistler Investment, for $220 million.

Reuters reported in early January that CVC was in talks with an adviser to explore the sale of its stake in the Ho Chi Minh-listed bank following approaches from potential buyers.

Investor interest in Vietnam, one of Asia's fastest growing economies, has increased as the country pursues an entry into emerging market indexes or an upgrade from FTSE Russell, with the country aiming for the inclusion by 2025. (Reporting by Phuong Nguyen in Hanoi, Kane Wu in Hong Kong and Yantoultra Ngui in Singapore; Editing by Christopher Cushing and Devika Syamnath)