The Swiss Reinsurance company reported on Wednesday that it expected to cover SFr1.2 billion ($723 million) in losses from the terrorist attacks on the United States.
Reinsurance companies insure insurance companies against major losses.
Swiss Re said in a statement from its Zurich headquarters that based on a first and very rough estimation, the loss to the company was expected to be in the range of the 1999 European winter storms Lothar and Martin.
"But further information will affect this indication," the statement added.
Swiss Re, whose share price fell by 17.3 per cent to SFr126.50 at the end of trading on Tuesday, said that given the unprecedented nature and complexity, it would take sometime to provide accurate information about the full extent of the event.
The statement said Swiss Re had many times in its history been faced with the consequences of large catastrophes and the company carried large provisions for "large catastrophic events of this magnitude".
"Even though this is one of the largest loss events possible, Swiss Re's financial strength is not in doubt and the fundamentals of the company will not change," the company statement said.
Swiss Re said it was "deeply moved by yesterday's tragic events in the United States".
"Swiss Re people have long-standing and often personal relationships with the financial and insurance community across the United States and particularly New York. Our thoughts and deepest sympathies are with them at this time," the statement added.
swissinfo with agencies