Swiss insurer Zurich Financial Services has said the five natural catastrophes to hit the Asia-Pacific region so far this year could cause claims of $500m (£310m).
The losses are net of its reinsurance cover, where other companies insure the cover it provides to companies, and before tax.
It follows three months of heavy claims losses for the global insurance industry as it grapples with earthquakes in Japan and New Zealand and floods across Australia in January.
"The charge for Japan is higher than we expected," said Kepler Capital Markets analyst Fabrizio Croce in a research note. His estimate for Zurich's hit had been below $100m.
Yesterday Lloyd's insurer Hiscox said it would take an $150m loss from claims from the Japan quake and tsunami alone, while reinsurer Swiss Re has said the disaster will cost it $1.2bn.