SINGAPORE, April 4 (Reuters) - Japan's Mitsui & Co said on Thursday it had teamed up with Rohto Pharmaceutical Co to buy Eu Yan Sang International in a deal valuing the Singapore-based traditional Chinese medicines firm at S$800 million ($594 million).

Mitsui said in a statement that a special purpose company jointly owned by Mitsui and Rohto would acquire around 86% of Eu Yan Sang from Righteous Crane Holding.

Righteous Crane Holding is owned by a fund managed by Tower Capital Asia, a unit of Temasek Holdings and founding family members of Eu Yan Sang, according to a separate statement issued by Tower Capital Asia on Thursday.

Following the deal, a takeover bid for the remaining 14% of Eu Yan Sang will be made, while the founding family of Eu Yan Sang will reinvest partially into the Misui-Rohto special purpose company, Mitsui added.

Reuters reported in January that Mitsui and Hillhouse had emerged as the final bidders vying for Eu Yan Sang.

Founded in 1879, Eu Yan Sang operates over 170 retail outlets and 30 clinics in Singapore, Hong Kong, and Malaysia, according to Mitsui's statement.

Righteous Crane Holding took the company private from the Singapore bourse in 2016. The deal valued Eu Yan Sang at about $196 million at the time.

Mitsui said it invested indirectly in Eu Yan Sang in November 2022. The Japanese firm added that it had contributed to the expansion of Eu Yan Sang's (EYS) business by helping to boost the company's brand and supporting overseas expansion.

"Through these activities, Mitsui reconfirmed EYS's strong business potential and how Mitsui could contribute to its business expansion," Mitsui said, adding this led to its decision to re-invest in Eu Yan Sang with Rohto and the founding family via the special purpose company.

The transaction is expected to close by June, according to Tower Capital Asia's statement.

Deutsche Bank and UBS are acting as financial advisers to Eu Yan Sang, with WongPartnership as the legal counsel, the statement showed.

($1 = 1.3467 Singapore dollars) (Reporting by Yantoultra Ngui# Editing by Mark Potter)