Mitsui Mutual Life Insurance Co. said Thursday that Sumitomo Mitsui Banking Corp. and other firms have agreed to plow a combined 100 billion yen into its foundation funds to improve its financial health.

As Mitsui Mutual's capital base, the equivalent of a shareholders' equity at ordinary companies, currently stands at 70 billion yen, the planned capital injection will more than double its size to 170 billion yen, according to Japan's seventh-largest life insurer.

Mitsui Mutual stopped short of identifying capital contributors -- other than Sumitomo Mitsui Banking -- and of specifying the respective amounts that will be contributed by each capital contributor.