Moody's Investors Service Inc. said Monday it has downgraded the insurance financial strength ratings of eight Japanese life insurance companies.

The ratings outlooks for the companies remain negative, the U.S. credit-rating agency said in a news release.

Moody's said it has downgraded the IFSR of both Daido Life Insurance Co. and Dai-Ichi Mutual Life Insurance Co. to Baa2 from A3.

Fukoku Mutual Life Insurance Co.'s IFSR was downgraded to Baa3 from A3, while that of Meiji Life Insurance Co. was downgraded to Baa2 from A2.

Mitsui Mutual Life Insurance Co. was downgraded to Ba3 from Ba1, and Nippon Life Insurance Co. to A3 from Aa3.

Sumitomo Life Insurance Co. was downgraded to Ba1 from Baa1, and Yasuda Mutual Life Insurance Co. to Baa2 from A2.

Meanwhile, Moody's said the Baa2 IFSR of Taiyo Mutual Life Insurance Co. remains unchanged, but its outlook has been changed to negative from stable.

"These downgrades and negative outlooks reflect worse-than-expected weakening of the financial conditions of these life insurers, the grim outlook for a quick recovery in the industry operating environment, the limited benefit of capital contributions planned, and the uncertain prospects for additional external support," the agency said.