Israel poisoned the late Yasser Arafat with the lethal radioactive substance polonium, a nephew of the veteran Palestinian leader alleged on Thursday.

But Israel denied the accusation, saying it was "not involved" in Arafat's death at a French hospital in November 2004.

"We accuse Israel of killing Yasser Arafat by poisoning him with that lethal substance," Nasser al-Qidwa told AFP, referring to polonium, traces of which were recently found on clothing worn by the ailing leader.

"Those responsible for that assassination should be held accountable and judged," said Qidwa, who is also president of the Yasser Arafat Foundation.

Allegations that the long-time Palestinian leader and Nobel Peace Prize laureate was poisoned were resurrected earlier this month after Al-Jazeera news channel broadcast an investigation in which experts said they had found high levels of polonium on his personal effects.

Polonium is a highly-toxic substance which is rarely found outside military and scientific circles.

The radioactive substance was used to kill former Russian spy turned Kremlin critic Alexander Litvinenko, who died in London in 2006 shortly after drinking a cup of tea laced with the poison.

But a spokesman for Israeli Prime Minister Benjamin Netanyahu completely rejected Qidwa's charge, denying any involvement in the ailing 75-year-old's death.

"Israel was not involved in the death of Arafat," Netanyahu's spokesman Mark Regev told AFP. "All the medical files are in the hands of the Palestinians and it was not Israel who is preventing their publication."

Until now, none of the medical files pertaining to Arafat's illness and death have been made public.

But on Thursday, the Arafat Foundation for the first time released all the medical files in its possession, many of them from the French military hospital where he was treated.

"Since the martyrdom of the late president Yasser Arafat, we have said that he was assassinated by poisoning but we have never had any tangible proof," Qidwa said.

"But since the Al-Jazeera documentary confirmed he was poisoned by polonium, there is no longer any doubt," he added.

Although experts at the Swiss laboratory which conducted the testing said they had found "significant" traces of polonium on Arafat's effects, they said there could be no confirmation he was poisoned without exhuming the body and examining his remains.

Senior Palestinian officials have said they would agree to an exhumation of the body, which is buried in the West Bank town of Ramallah, if the family gave its permission, and Qidwa on Thursday said they would raise no objections.

"The Arafat Foundation contacted the Swiss laboratory and informed them that it had no objection to analysing samples from the body of the late Palestinian president Yasser Arafat if it is necessary," he said.

Last week, Arafat's widow Suha also said she was in favour of allowing tests on her husband's remains.

At the time of his death, she had refused to permit an autopsy.

The Palestinians have called for an international probe into Arafat's death based on the findings of Al-Jazeera's nine-month investigation which centred on the forensic testing of his personal effects handed to Suha by the French hospital where he died.

Traces of Arafat's hair as well as his sweat, urine and blood were found in his effects and on his clothing, all of which were sent for testing at several European laboratories.

Francois Bochud, head of the Institute of Radiation Physics at the University of Lausanne who participated in the investigation, told Al-Jazeera that tests on Arafat's remains would need to be done as soon as possible.

"We have to do it quite fast because polonium is decaying, so if we wait too long, for sure any possible proof will disappear."

It was not immediately clear when any exhumation process would take place.

Arafat, who led the struggle for Palestinian statehood for nearly four decades, died in a French military hospital on November 11, 2004 after being airlifted there for treatment from his Ramallah headquarters.

At the time of his death, Palestinian officials alleged he had been poisoned by long-time foe Israel, but an inconclusive Palestinian investigation in 2005 ruled out poisoning, as well as cancer and AIDS.

Israel has consistently denied the allegations, accusing Suha Arafat and Palestinian officials of covering up the real reasons for the former leader's death.