Tests conducted by a team of Swiss experts on Arafat's body showed "unexpected high activity" of polonium.
Hamas has accused Israel of assassinating late president Yasser Arafat after a Swiss forensic report showed that the iconic leader may have been poisoned with radioactive polonium.
"The forensic report shows that Arafat's death was not natural and that he was assassinated," Hamas spokesperson Sami Abu Zuhri told Anadolu Agency on Wednesday.
"Hamas accuses the Israeli occupation of being behind the assassination," he added.
Arafat, 75, died in France in 2004, but doctors were unable to specify the cause of the death.
His remains were exhumed in November 2012 and tests conducted by a team of Swiss experts on his body showed "unexpected high activity" of polonium.
Abu Zuhri called on the Palestinian Authority to halt peace negotiations with Israel and to launch investigations into the death.