Natural disasters, including the March earthquake and tsunami, cost insurers about $60 billion in the first half of this year, almost five times the average since 2001, Munich Re said.
"Most of the losses were accounted for by the earthquake in Japan," the Munich-based company said in an emailed statement Tuesday.
The total economic losses of $265 billion in the period exceeded the figure for all of 2005, previously the costliest year on record.
Insurers such as Allianz SE and Axa SA and reinsurers, which help them shoulder risks for clients, had their most costly first quarter this year because of disasters, including the earthquake and tsunami that devastated the Tohoku region in March, a cyclone and floods in Australia and the quakes that hit Christchurch in New Zealand in February and June.
The Japan quake caused an overall economic loss of $210 billion, making it the costliest natural catastrophe on record, Munich Re said. Losses assumed by insurers, which Munich Re estimates at $30 billion, will not reach the $62.2 billion caused by Hurricane Katrina in 2005, the reinsurer added.
Typically, the first six months of a year see lower insured losses than the final six months, which are often affected by hurricanes in the North Atlantic and typhoons in the Northwest Pacific, Munich Re said.
No major hurricane has hit the U.S. coast so far this year. Forecasts suggest the 2011 Atlantic season will be more active than in an average year, which produces 11 named storms.
Hurricanes are watched closely because they are a threat to oil and natural gas interests in the Gulf of Mexico and agriculture in the Deep South.
Florida is the second-largest citrus producer behind Brazil, while the gulf accounts for 31 percent of U.S. oil output and 43 percent of refining capacity.