Authorities are focussing on how big business operates

Andreas Kley, 63, and Horst Vigener, 73, who used to work at Siemen's power generation unit, face charges of bribery and breach of trust.

It is claimed they made payments to win contracts for gas turbines from Italian utility Enel between 1999 and 2002.

Siemens is also involved in a larger, separate bribery scandal.

Investigations

Another six current and former Siemens executives are caught up in a different case, with German police saying in February that they would investigate allegations that Siemens had a 200m-euro slush fund to help win contracts.

The company also is being probed by the US Department of Justice, and the Securities and Exchange Commission.

For its part, Siemens said it had found suspicious payments worth some 420m euros, and is carrying out its own investigation.

It has hired an outside anti-corruption expert and a law firm to examine and revise Siemens' own anti-corruption safeguards.

Speaking last month, Siemens chief executive Klaus Kleinfeld denied any knowledge of the alleged corruption and said that "we do not tolerate illegal business practices and that is not negotiable".