ZURICH (Bloomberg) — Shares of Zurich Financial Services AG, Switzerland’s biggest insurer, rose amid speculation that the company may be the target of a takeover bid.Zurich Financial’s stock climbed as much as 2.6 percent to 354 Swiss francs and closed at 350 francs in Zurich, a 1.4 percent gain and the biggest rise for the shares since March 22. The insurer is now valued at 50.7 billion francs ($41.6 billion).

“There are rumours that someone is offering 400 francs a share,” Rene Locher, a senior insurance analyst at Bank Sal. Oppenheim in Zurich, said in a telephone interview.

Last year’s sale of Credit Suisse Group’s Winterthur insurance unit and this year’s hostile bid by Scor SA for Swiss reinsurer Converium Holding AG are fuelling speculation about takeovers in the industry. US-based St. Paul Travelers Cos. in September denied a newspaper report that said it held merger discussions with Zurich.

A spokesman for the Zurich-based insurer, Angel Serna, said the company “doesn’t comment on market rumours. This is a rumour.”

Zurich in February reported a 41-percent increase in full-year earnings to a record. Chief executive officer James Schiro said then that the company has “enough cash for further growth, be it organic or non-organic.”

“Everything is plausible but I would take it more as a rumor than something real,” said Marc Effgen, an analyst at Helvea AG in London. He estimates the “fair value” of Zurich Financial is 405 francs a share. “It’s difficult in this kind of environment as a lot of companies have a lot of excess cash and little growth.”