Receipts, the launch of which it announced in May, started trading over the counter in the US on Monday.

Switzerland's biggest direct insurer said the ADRs, which are US traded securities that represent claims to shares of foreign stock, represent one fifth of a registered share.

"Zurich's primary goal is to make it easier for US investors to purchase Zurich common shares,'' said Chief Financial Officer Rolf Haenggi, in a prepared statement.

The move comes after the insurance company expanded its US business in recent years, including last year's acquisition of Illinois-based Kemper Corp., a life insurer and asset manager.

Zurich also part-owns Zurich Reinsurance Centre Inc. and the Bermuda-based Centre Re group of companies.