By Steve Gutterman

MOSCOW (Reuters) - Russia said on Thursday former Palestinian leader Yasser Arafat died of natural causes, not radiation poisoning, but a Palestinian official called the finding "politicized" and said an investigation would continue.

Samples were taken from Arafat's body last year by Swiss, French and Russian forensics experts after an al Jazeera documentary said his clothes showed high amounts of deadly polonium 210.

The Swiss said last month their tests were consistent with polonium poisoning but not absolute proof of the cause of death. The Russian finding was in line with that of French scientists who said earlier this month that Arafat had not been killed with polonium.

"Yasser Arafat died not from the effects of radiation but of natural causes," Vladimir Uiba, head of Russia's state forensics body, the Federal Medico-Biological Agency, was quoted as saying by the Interfax news agency.

Arafat, who signed the 1993 Oslo interim peace accords with Israel but then led an uprising in 2000, died at 75 at the Percy hospital in Paris in 2004, four weeks after falling ill in his Ramallah compound, which was surrounded by Israeli tanks.

"Like the French report on his death, this is a politicized finding. The truth lies at the Percy hospital," Wasel Abu Yousef, a senior member of the Palestine Liberation Organisation, told Reuters.

The official cause of death was a stroke, but French doctors said at the time they were unable to determine the origin of Arafat's illness. No autopsy was carried out.

His widow, Suha Arafat, has argued the death was a political assassination by someone close to her husband. Many Palestinians believe Israel killed him - a charge Israel denies.

The Palestinian ambassador to Moscow, Faed Mustafa, said the Russian findings would not halt efforts to investigate the cause of death, state-run Russian news agency RIA reported.

"I can only say that there is already a decision to continue (investigating)," RIA quoted him as saying. "We respect their position and we highly value their work, but there is a decision to continue work."

(Additional reporting by Ali Sawafta in Ramallah; editing by Andrew Roche)