LONDON (Bloomberg) — Catlin Group, the biggest insurer on the Lloyd's of London market, and Brit Insurance Holdingsrose as concerns receded about their possible losses from the collapse of US subprime mortgages.

Catlin shares advanced as much as 6.1 percent and traded up 3.9 percent to 417 pence while Brit shares gained as much as 5.6 percent and traded up 3.5 percent to 240 pence in London during yesterday afternoon.

"We have spoken to management and we have a lot more confidence about the potential exposure to the subprime issue," said Richard Gradidge, an analyst at Numis Securities in London, referring to both companies. There have been "fears" regarding Brit's underwriting of subprime-related claims by financial companies and on Catlin's holdings of subprime related assets, he said. Gradidge has a "buy" rating on both stocks.

Spokesmen for Catlin and Brit declined to comment.