UPDATE 1-Japan's Chubu Electric to buy 20% stake in Vietnam renewable energy firm Bitexco

(Adds background, comments)

TOKYO, Sept 28 (Reuters) - Japanese utility Chubu Electric Power Co Inc said on Tuesday it will buy a 20% stake in Vietnamese renewable energy firm Bitexco Power Corp for an undisclosed sum, to gain a foothold in the growing market and expand its portfolio of green energy.

The move comes a day after its joint venture with Tokyo Electric Power Company Holdings Inc, JERA, said it will invest $1.58 billion to take a 27% stake in Aboitiz Power Corp in the Philippines to boost its presence in the country where power demand is growing.

"Our goal is to expand our overseas business by tapping into the growth of Vietnam's electricity market while contributing to the decarbonisation of Vietnam," Akihide Ito, general manager at Chubu Electric, told a news conference.

Bitexco is a leading renewable energy company in Vietnam focused on hydropower and solar, operating 21 hydropower stations and one solar power plant, with a generation capacity of about 798 megawatts (MW), Chubu said.

The Japanese utility aims to help improve the operating efficiency of Bitexco's hydropower stations and support the Vietnamese company's plans to expand solar capacity and develop onshore wind farms.

Under the deal, Chubu will purchase the stake from Japan's Orix Corp and Singapore's United Overseas Bank , and will buy new shares to be issued by Bitexco, Ito said.

Japanese trading house Mitsubishi Corp and Chubu bought Eneco last year in a deal valuing the Dutch energy firm at 4.1 billion euros ($4.8 billion).

"We will continue to expand our overseas business, mainly in Europe and Asia," Ito said.

($1 = 0.8537 euros) (Reporting by Yuka Obayashi; Editing by Kim Coghill and Mark Porter)