"The Russians, they make claims without providing any data, without providing any scientific arguments, for me that is empty, a political declaration," said Francois Bochud, director of the Lausanne Radiophysics Institute.

Vladimir Uiba, the head of Russia's Federal Medical-Biological Agency (FMBA), told a news conference in Moscow on Thursday that Arafat "died a natural death and not from radiation."

Bochud criticized the Russians for not releasing their report.

Bochud was the co-author of a report released on November 7 that found high levels of polonium, up to 20 times the normal level. It said the findings were consistent with radioactive poisoning.

Arafat died in France on November 11, 2004 at the age of 75, but doctors were unable to specify the cause of death. No autopsy was carried out at the time, in line with his widow's request.

His remains were exhumed in November 2012, partly to investigate whether he had been poisoned with radioactive polonium, a suspicion that grew after the substance was used to assassinate Russian ex-spy and Kremlin critic Alexander Litvinenko in 2006.

This is "totally false", Bochud told AFP. "Our point of view has not changed, that's for sure."

Bochum said that the Swiss had not received a copy of the Russian study, and that Palestinian officials who had seen it said the results were similar to the Swiss data.

"But to claim the opposite with same data seems to be really fallacious," said Bochud.

SHI/SHI