Business insurer XL Group plc last night announced a first-quarter net loss of $227.3 million after it was hit by catastrophe losses of more than $380 million in the first three months of the year.The net operating loss of $163 million, or 52 cents per share, was more severe than the 46 cents per share expected by a panel of analysts polled by Bloomberg.Natural catastrophe losses from events including the Japan earthquake and tsunami, February’s New Zealand earthquake and January floods in Australia cost the company an estimated $387.4 million, net of reinstatement premiums, during the quarter.“XL’s first-quarter results demonstrate resilience in the face of global catastrophic events,” XL CEO Mike McGavick said in a statement.“We are proud of the roles our insurance and reinsurance solutions are playing in the recovery of the devastated economies. Our risk management discipline again resulted in estimated losses from the quarter’s three major catastrophes that are well within our expected levels.“As markets respond to these events and others, we believe our underwriting excellence, operating efficiency and capital strength put XL in an exceptional position to pursue the opportunities provided by improving market conditions.”Losses attributed to the Japan disaster totalled $242.6 million, while the Australian floods cost the firm $66.9 million and the Christchurch earthquake generated net claims of $75.3 million.The combined ratio for the quarter - indicating the proportion of premium dollars paid out in claims and expenses - was 125.8 percent for property and casualty operations.Fully diluted book value per ordinary share was $29.03 at March 31, 2011, a decrease of 2.5 percent during the quarter. During the quarter, XL purchased 7.3 million shares for $165.6 million at an average price of $22.83, which was accretive to book value per ordinary share by 14 cents.Gross written premiums increased by 9.2 percent compared to the prior-year quarter as a result of select new business growth and exposure increase in certain lines linked to economic growth.The increase was driven by an increase in the Insurance segment of eight percent and the reinsurance segment of 10.9 percent, XL said. Improving economic conditions, the renewal of certain multi-year accounts and select new business initiatives drove insurance premium growth. On the reinsurance side, growth came specifically from opportunities in Europe, principally the UK motor market, marine and some increases in the Continental European catastrophe portfolio.Net investment income for the quarter was $280.3 million compared to $308.3 million in the prior-year quarter. The decline was primarily due to lower US interest rates and cash outflows from the invested portfolio.Net investment income from investment affiliates contributed $27.2 million in the quarter, up from $8.2 million in the same period in 2010 as a result of strong private investment returns.XL said net realised investment losses for the quarter were $66.4 million compared to $36.2 million in the prior year quarter. The losses related primarily to losses on sales of European hybrid securities and impairments on below investment grade non-agency residential mortgage-backed securities.