Insured loss estimates from the Melbourne hailstorm on March 6 have risen 68% in little over a week to $830 million.

Insurance Council of Australia figures released on Friday show insurers have received 105,000 claims at a total cost of $830 million.

The storm sent golf-ball sized hailstones into homes, cars and businesses in one of the biggest natural catastrophes to hit urban Melbourne in decades.

A subsequent hailstorm in Perth and earlier cyclone and flooding events in Queensland threaten to wipe out underwriting profitability for domestic insurers.

The storms in Melbourne and Perth have prompted IAG to twice revise its full-year insurance margin guidance, which is now forecast to fall between 9.5-11% against an original estimate of 11.5-13%.