Nippon Life Insurance Co. is in talks to purchase a stake in India's Reliance Life Insurance Co. to boost business overseas, a source said.

Japan's biggest life insurer may acquire a 26 percent stake in Mumbai-based Reliance Life for ¥60 billion ($720 million), said the source, who spoke on condition of anonymity because the information hasn't been made public.

Japanese life insurers, mostly mutual societies owned by policyholders, are expanding abroad to offset slowing premium growth in a home market where the birthrate is declining and the average age is increasing at the world's fastest rate.