LONDON (Bloomberg) - Gjensidige Forsikring BA, Norway's largest property and casualty insurer, plans to start canvassing investor interest in its initial public offering as soon as this week, two people with knowledge of the matter said.

The IPO may raise more than $1.5 billion, said one of the people, who declined to be identified before an official announcement. The offering would be the country's biggest since at least 2006, data compiled by Bloomberg show.

The customer-owned insurer proposed in March that it become a publicly traded company, following legislation in Norway that allows such companies to organize clients' ownership into financial foundations. The company is planning to sell a stake of as much as 40 percent, chief financial officer Tor Loennum said on August 19.

Oeystein Thoresen, a spokesman for Gjensidige, declined to comment. Goldman Sachs Group Inc. is sole global coordinator for the IPO, while Bank of America Corp., DnB NOR ASA, Pareto Securities and Keefe, Bruyette & Woods Inc. will also help manage the sale, according to Loennum.

The Norwegian insurer has been seeking to boost revenue by expanding outside its home country. The company agreed in March to buy Nykredit Realkredit A/S' non-life insurance division for 2.5 billion kroner ($430 million) to add 230,000 clients in Denmark, its seventh takeover outside Norway since 2006. It also bought Citigroup Inc.'s consumer finance operations in Norway last year and purchased Lithuania's RESO Europa in 2008 to expand its market share in the Baltics.

Statoil Fuel & Retail ASA, the gas station and fuel unit of oil and gas producer Statoil ASA, raised $920 million in Oslo's biggest IPO this year.