NEW YORK (Bloomberg) - XL Capital Ltd., the Bermuda-based business insurer that bailed out bond guarantor Syncora Holdings Ltd., said it lost $1.62 billion in the third quarter on a charge tied to the rescue - confirming its estimations given in preliminary results last month.

Book value per share, a measure of assets minus liabilities, fell by half in the three months ended September 30 to $21.65 after the insurer sold stock and investment losses depleted capital, XL said in a regulatory filing after the markets closed on Monday.

Book value fell from $43.39 per share during the quarter and from $56.29 over 12 months.

The net loss of $6.09 a share compares with profit of $371.6 million, or $1.82 a share, in the same period a year earlier and was within the range XL gave when it released preliminary results on October 14.

Chief executive officer Michael McGavick, hired in March, said he is seeking to eliminate "big mistakes," like XL's entanglement with Syncora, and focus on underwriting. The firm had $292.9 million in investment losses, and unrealised losses widened by $825.3 million.

"It was a tough quarter by any measure," McGavick said on October 14. The release of the final numbers was not accompanied by a new statement. XL's share price rose 51 cents, or five percent, to $10.71 in New York Stock Exchange composite trading yesterday. It has declined 80 percent this year compared with the 47 percent decline in the 84-stock Standard & Poor's Financials Index. Results were released after the close of regular trading.

XL estimated it lost $221.8 million on hurricanes Gustav and Ike, which struck the US Gulf Coast in September.

Unrealised losses on the firm's holdings of asset- and mortgage-backed securities rose 26 percent to $1.47 billion in the three months ended September 30. Unrealised losses on corporate debt widened 34 percent to $1.68 billion.

XL sold more than $2.8 billion in stock in part to rescue the insurance operations of Syncora, the company it co-founded and then spun off. Syncora, formerly known as Security Capital Assurance Ltd., faced a wave of claims after collateralised debt obligations it insured declined in value.