Farouk Kaddoumi, head of the Palestine Liberation Organization's mainstream Fatah faction, said Arafat was poisoned by Israel "because he was a stumbling block to (Israeli) plans." Other Palestinians have made the same charge in the past and Israel has repeatedly denied it.
The PLO will ask the U.N. Security Council "to form an international investigating commission into the assassination of Palestinian leader Yasser Arafat." Kaddoumi told reporters on Saturday.
Arafat died in a French hospital on Nov. 11, 2004 at age 75. The exact cause of death remains unknown, fueling persistent rumors that he was either poisoned or died of AIDS.
Kaddoumi was speaking in Damascus after meeting representatives of the Syria-based radical Palestinian factions opposed to the PLO's peace accords with Israel. He said all Palestinian groups are united in holding Israel fully responsible for Arafat's death.
The Percy Military Hospital, which treated Arafat, has not clarified the cause of death, and its medical records, recently leaked to reporters, have proven inconclusive.
Those records, obtained by two Israeli journalists who shared them with The Associated Press, cast doubt on the conspiracy theories. French doctors who treated Arafat at Percy concluded he died of a "massive brain hemorrhage" after suffering intestinal inflammation, jaundice and a blood condition known as disseminated intravascular coagulation, or DIC.
But the records are inconclusive about what brought about DIC, which has numerous causes ranging from infections to colitis to liver disease.
On Friday, the Palestinians in the West Bank marked the first anniversary of Arafat's death. Arafat's nephew, Palestinian Foreign Minister Nasser al-Kidwa, said at the time he is convinced his uncle did not die of natural causes, and that Israel killed him.
Two Palestinian government panels are already investigating the circumstances surrounding Arafat's death.