In September, Reuters exclusively reported sources as saying that Vingroup was considering selling controlling stakes in both Vinmec and Vinschool, the group's educational unit. At the time, Vingroup said it had no plans to sell stakes in Vinmec or Vinschool.

Monday's press statement said Vingroup would remain the controlling shareholder of Vinmec. A Vingroup spokesman declined to say how large a stake had been sold, citing the "commitment between two sides".

Vinmec operates seven hospitals and five clinics in Vietnam. Credit Suisse acted as the sole advisor to Vingroup, the company said.

Founded by Vietnam's richest man, billionaire Pham Nhat Vuong, Vingroup is omnipresent in the Southeast Asian country.

Just a year ago, one could be born in a Vinmec hospital, go to a Vinschool, live in a Vinhomes apartment and drive to a Vinmart in a Vinfast car.

However, the group sold Vinmart last year, and with the stake sales of Vinmec, Vingroup is scaling back its sprawling business after a rapid expansion created a big debt burden.

(Reporting by Phuong Nguyen; Additional reporting by James Pearson; Editing by Louise Heavens and Susan Fenton)