Moody's Investors Service said Friday it has lowered its financial strength ratings of four Japanese nonlife insurance companies in light of difficult operating conditions, especially since the July 1 liberalization of premium pricing.

The new ratings are Aa1 from Aaa for Tokio Marine & Fire Insurance Co. and Aa2 from Aaa for Yasuda Fire & Marine Insurance Co., Mitsui Marine & Fire Insurance Co. and Sumitomo Marine & Fire Insurance Co., Moody's said.

The major U.S. rating agency also downgraded Sumitomo's senior unsecured debt and long-term issue ratings to Aa2 from Aaa. Moody's said the latest rating action reflects its view that anticipated reductions in insurance premium rates are likely to have substantial negative implications for the four firms' current financial strength.

In addition, the four insurers are exposed to various negative environmental pressures, such as falling stock prices in Japan and the increasing credit risk that is affecting Japanese industrial firms and financial institutions, Moody's said.