Insured losses from floods in Japan last month could reach $US4 billion ($5.4 billion), AIR Worldwide says.

The floods were the worst in more than 30 years, with record downpours in the west and south-central regions.

At least 200 people died in the country’s deadliest natural catastrophe since the 2011 earthquake and tsunami.

Modeller AIR’s estimates include damage to property, contents and vehicles, but not losses in a number of areas including land, infrastructure and business interruption.