Vienna  - Animal rights activists have claimed responsibility for burning down an Austrian house owned by the chief of pharmaceutical giant Novartis, triggering a probe by the anti- terrorism agency, the Interior Ministry said Thursday.

The fire at Daniel Vasella's hunting lodge on Monday followed a recent string of attacks against his Swiss-based company, including the theft of the ashes of Vasella's mother in late July.

A group called Militant Forces against Huntingdon (MFAH) Austria claimed it started the blaze because of Novartis' alleged cooperation with a major British company conducting tests on animals.

"It hasn't been your week has it, Daniel?" MFAH wrote on the US- based website www. directaction. info. "This will continue until you severe all ties with Huntingdon Life Sciences."

The activists claimed they placed 60 litres of petrol around Vasella's house, which was part of his hunting estate in the Tyrol mountains.

Novartis employees and facilities in Switzerland have been targeted by animal rights extremists in recent months. Swiss media reported that the Britain-based group Stop Huntingdon Animal Cruelty (SHAC) was likely behind those attacks.

SHAC denied any involvement in the series of attacks and said it was a "legal, grassroots campaigning group."

"(If it was actually done by animal rights people), it's because of their frustration" of Novartis' work with Huntingdon Life Sciences, SHAC said in a statement, accusing the animal testing firm of cruel and sloppy practices.

Neither Novartis nor Huntingdon make their cooperation partners public.

"The awful attacks on Mr Vasella, if they are animal-rights motivated, should be condemned," Huntingdon's spokesman told the German Press Agency dpa. He did not want his name to be published.

Huntingdon Life Sciences is one of the largest European companies that conducts animal experiments for pharmaceutical companies. Huntingdon Life Sciences was targeted by militants from 2000 to 2002, its spokesman said.

Austria's police intelligence agency, which is also involved in anti-terrorism work, has contacted authorities in Switzerland and Germany about the case.

MFAH Austria had so far not been known in Austria, Interior Ministry spokesman Alexander Marakovits said.

"We are in the process of analyzing the claim of responsibility to see whether it is authentic," he said. (dpa)