new york (Bloomberg) — Assured Guaranty Ltd., the bond insurer backed by billionaire Wilbur Ross, rose the most in more than five months in New York trading after reporting first-quarter profit that topped analysts' estimates.

Assured climbed $2.59, or 23 percent, to $13.72 at the close of New York Stock Exchange composite trading on Friday, after earlier touching $3.17, the biggest intraday percentage increase for the Hamilton, Bermuda-based company since November 24.

The net income was $85.5 million compared with a loss of $169.2 million a year earlier.

"I am pleased by the results for the first quarter," chief executive officer Dominic Frederico said on the call. "I continue to be optimistic about the remainder of 2009."

Assured has benefited from a jump in its market share as ratings firms and issuers deem competitors including MBIA Inc. and Ambac Financial Group Inc. as more troubled, even as Assured's own risks mount. Fitch Ratings stripped its AAA insurance grade four days ago, following Moody's Investors Service.