Yasser Arafat was poisoned to death in 2004 with radioactive polonium, according to the results of a Swiss forensic team which took samples from the former Palestinian leader's exhumed body.
ITV News Middle East Correspondent Geraint Vincent reports:
A team of experts, including from Lausanne University Hospital's Institute of Radiation Physics, opened Arafat's grave in the West Bank city of Ramallah last November, and took samples from his body to seek evidence of alleged poisoning.
Arafat fell ill in October 2004, displaying symptoms of acute gastroenteritis with diarrhoea and vomiting. At first Palestinian officials said he was suffering from influenza.
He was flown to Paris in a French government plane but fell into a coma shortly after his arrival at the Percy military hospital in the suburb of Clamart, where he died on 11th November.
The official cause of death was a massive stroke but French doctors said at the time they were unable to determine the origin of his illness and no autopsy was carried out.
Arafat's widow, Suha, has described her anger and distress at the news.
Mrs Arafat said: "Words can't express my deep sorrow and the sorrow of my daughter, but mostly the anger - we are so angry. It's a political crime, a political assassination. It is so hard, we are mourning him again."
"We are revealing a real crime, a political assassination," Suha told Reuters.
"This has confirmed all our doubts. It is scientifically proved that he didn't die a natural death and we have scientific proof that this man was killed."
Hanan Ashrawi, who was close to Arafat and saw him shortly before he left for Paris has joined other voices blaming Israel for his death.
She said: "All along we thought that it was Israel. This is a very familiar pattern unfortunately in our part of the world. Where Israel has assassinated Palestinian leaders at will and has got away with it."
The Israeli government has denied any role in the death of Yasser Arafat, saying that he was 75-years-old.
"This is more soap opera than science, it is the latest episode in the soap in which Suha opposes Arafat's successors," Israeli Foreign Ministry spokesman Yigal Palmor said.
The investigation amounted to "a highly superficial attempt to determine a cause of death".