Novartis chief executive Daniel Vasella has branded as terrorists the animal rights activists who set fire to his Austrian holiday home and previously desecrated the graves of relatives, stealing the remains of his mother.

Speaking on CNBC television, Dr Vasella said that “when you try to terrorise people and you burn their houses, when you desecrate graves and when you make death threats, to me that is way beyond activism and I would clearly call this terrorism." He added that “it's highly unpleasant, to say the least, to be attacked so directly and threatened”, saying that “of course, the objective is to terrorise and to instil fear”.

The CEO and his family were not at home last week when the entrance and exit of the house in Austria were doused with 15 gallons of gasoline and then set alight. Dr Vasella noted that “it has been difficult, especially for the kids”, who are aged between 17 to 25, “but we deal with it."

The fire comes after criminals stole an urn last month containing the ashes of his mother in the Swiss city of Chur and painted a message on a family gravestone saying “Drop HLS Now”, a reference to the animal-testing business Huntingdon Life Sciences. Novartis cut its links to the latter group a long time ago

Mr Vasella told CNBC that the attacks on the graves brought back “the losses I experienced, especially my sister when she died of cancer” and of his father who passed away when he was 13. He added that “all these memories come up and, of course, that's the intention. So, you try to deal with it in a rational way but without denying the feelings."

The Austrian authorities said that a group called Militant Forces Against Huntingdon Life Sciences has claimed responsibility for the attacks, though police had claimed it had found no evidence for an arson attack on Dr Vasella's home. Investigations are continuing.

Dr Vasella had earlier told the SonntagsBlick Swiss weekly newspaper that he understood the concerns of legitimate animal rights activists but told CNBC that “these people try to hinder medical progress” and stand in the way of finding new treatments.