SEOUL—Prosecutors have indicted a former chief executive of the South Korean unit of Novartis and five other former and current managers over allegations they illegally paid doctors 2.6 billion won ($2.3 million) in return for prescribing the company’s drugs.

In response, the Swiss pharmaceutical company expressed regret through a statement, but said such conduct wouldn't have been sanctioned by the “most senior management” at Novartis Korea.

...