Japan's Nippon Life Insurance said on Thursday it has agreed to buy a 26 percent stake in a fund management unit of Reliance Capital for about $290 million as Japanese insurers accelerate a push to tap Asia's emerging economies.

Reliance Capital, controlled by billionaire Anil Ambani, agreed in March last year to sell a 26 percent stake in its life insurance business Reliance Life Insurance to Nippon Life for $680 million, valuing the business at $2.6 billion.

Nippon Life, Japan's largest life insurance firm by premium income, said it would pay 14.5 billion rupees to buy the stake in Reliance Capital Asset Management.

"The Indian mutual fund market has grown rapidly since it was opened to the private sector in 1993," it said. "It is an attractive market that is expected to achieve robust growth in the long term due to the second-largest population in the world and solid economic growth led by the service sector and domestic consumption," it said.

Based in the world's second-largest market, Japanese life insurers have been almost entirely focused on their home turf, but are starting to look for opportunities elsewhere.

Meiji Yasuda Life Insurance Co., Japan's second-largest player, told Reuters earlier this week, it want to acquire one or two overseas companies in emerging economies this year, with Thailand, Vietnam and India particularly attractive in Asia.