Daniel Vasella, chief executive of the Swiss pharaceutical group Novartis, is fighting back against animal rights activists who are waging a campaign of intimidation against the company.

Vasella has warned about 140 people who sent him critical e-mails that they are associating themselves with criminal activity. Extremists desecrated his family grave in July. His comments are the most aggressive response yet by a senior pharmaceutical executive. Most have preferred not to engage in public debate with extremeists.

The animal rights activists demand that Novartis sever links with Huntingdon Life Sciences, the UK-based animal testing center. They warned Vasella that otherwise they would not return an urn containing the ashes of his grandmother.

Vasella defends the company’s commitment to researching medicines and stresses his commitment as a doctor to alleviating patient suffering, and says anyone who tries to stop medical progress should be “ashamed.”

"We strongly condemn the use of violence and terrorist tactics as a substitute for meaningful, productive dialogue,” Vasella said. “As the author of the e-mail received, you should be aware that willingly or not you are associating yourself with criminal activity, such as extortion and blackmail."