(Adds size of stake in second paragraph.)

July 1 (Bloomberg) -- Citigroup Inc. is buying a stake in Vietnam’s Horizon Securities Corp., according to two people with knowledge of the matter.

The U.S. bank agreed to acquire 9.9 percent of closely held Horizon for an undisclosed amount yesterday, the two people said, declining to be identified before a public announcement.

The transaction was reported earlier today by the Wall Street Journal.

--Diep Ngoc Pham, Joyce Koh with assistance from Giang Nguyen and Nicholas Heath in Hanoi. Editor: Chitra Somayaji

To contact the reporter on this story: Diep Ngoc Pham in Hanoi at dpham5@bloomberg.net; Joyce Koh in Singapore at jkoh38@bloomberg.net

To contact the editor responsible for this story: Chitra Somayaji at csomayaji@bloomberg.net; Philip Lagerkranser at lagerkranser@bloomberg.net