Shares in Germany's Siemens AG (NYSE: SI) rose over 4 percent on Friday after its supervisory board chairman said he would step down yesterday as the company tries to restore its image in the midst of a series of bribery and corporate corruption accusations.

Chairman and former CEO, Heinrich von Pierer, who has not been the subject of investigations, said late Thursday he would resign from Siemens for the good of the company, not because he has been involved in the alleged corruption.

Employees, including executives, at electrical and engineering conglomerate have been charged or detained in criminal investigations over events which took place during Pierer's 12-year tenure as chairman. In one wide-ranging case, the firm is said to have paid over $500 million in bribes to win telecom contracts.

I have always believed that one's duty to the company and its well over 400,000 employees worldwide must take priority over one's own interests, Pierer said in a statement. A personal responsibility regarding the current investigations was not the basis for my decision.

U.S. traded shares of the firm conglomerate rose $4.10, or 3.5 percent, to $122.60 on the New York Stock Exchange.