US insurers are facing a $US3.35 billion ($3.55 billion) first-quarter claims bill from catastrophes, more than double the $US1.26 billion ($1.34 billion) payout for the corresponding period last year, according to the Insurance Services Office (ISO).

The nine events detailed in the report by the ISO’s Property Claims Services Unit represent the greatest frequency of cats since 1999.

Personal lines accounted for 56% of total losses, with commercial lines totalling 31% and the remaining claims coming from insured vehicle losses.