Allianz, the German insurer which employs more than 4,000 people in the UK, said it expects floods across central Europe to cost it about €350m (£298m).
The company is likely to pay out more than €500m to its policyholders, although about €150m of this will be passed on to reinsurers.
Rivals Munich Re and Hannover Re have said it is too early to give estimates of their liabilities.
Swaths of cities such as Prague were left under water after floods swept across the region. The deluge moved towards Germany, where more than 10,000 people have been forced from their homes.
The last time central Europe saw similar floods was in 2002, when 17 people were killed in the Czech Republic, and damage estimated at €20bn was inflicted across the region.
In Germany alone, it is estimated damage could reach €12bn, of which insurers could shoulder up to £3bn.
- More about: