At 0838 GMT the Swiss Market Index of the twenty most traded stocks was up 3.79 percent to 5,338.14 points.

Meanwhile, the Swiss franc, which had risen strongly in response to the eurozone debt crisis, plunged 9.32 percent to 1.212 francs per euro, after the Swiss National Bank’s currency peg announcement.

The central bank said in a statement that “with immediate effect, it will no longer tolerate a EUR/CHF exchange rate below the minimum rate of CHF 1.20.”

“The current massive overvaluation of the Swiss franc poses an acute threat to the Swiss economy and carries the risk of a deflationary development,” the SNB said.

Global offshore drilling group Transocean led the surge, climbing 9.29 percent to 43.42 francs per share, followed by watchmaking giant Swatch, which rose 5.87 percent to 351.60 francs, and temporary staffing agency Adecco, which increased 5.47 percent to 33.91 francs per share.

Banks also fared well despite continued fears over a tax dispute with the United States. Julius Baer was up 4.58 percent to 30.11 francs per share, followed by UBS which rose 4.55 percent to 10.79 francs, and Credit Suisse climbed 3.55 percent to 20.70 francs per share.

The Swiss economy is heavily dependent on exports, notably to the eurozone, and on tourism. The rise of the Swiss franc as a safe haven instrument in the latest twist of the eurozone debt crisis is hitting the Swiss economy hard.

Switzerland is not a member of the European Union and so is not a member of the eurozone.