SWISS Reinsurance Co, the world's biggest reinsurer, said profit fell a more-than-estimated 53 percent after a decline in premiums and 819 million Swiss francs (US$778 million) of credit market writedowns.

Swiss Re dropped as much as 6.2 percent in Zurich trading, the most in more than three months, after the company said it would book a further 200 million francs of writedowns because of the difficult market environment.?

First-quarter net income declined to 624 million francs, or 1.84 francs a share, falling short of the 870-million-franc estimate of nine analysts surveyed by Bloomberg News.

?¨Credit losses are unexpectedly high,? said Viktor Dammann, an analyst at Bank Vontobel in Zurich with a hold? rating on the stock.

?¨I??d rather hoped to see some stabilization in this market, but this stuff is on the books and you just can't get rid of it.?

Chief Executive Officer Jacques Aigrain said yesterday in a statement that the Zurich-based reinsurer's capital position remains strong,? even as derivatives-related losses increase.

Reinsurance rates, which soared after Hurricane Katrina hit the US Gulf Coast in 2005, have fallen for two years and caused premium income to drop 20 percent in the first three months of this year.

Chief Financial Officer George Quinn raised the possibility that Swiss Re may fall short of its profit growth target of 10 percent and return on equity of 14 percent.