Palestinian movement Fatah has accused Gaza's rulers Hamas of banning it from commemorating Monday's ninth anniversary of Palestinian leader Yasser Arafat's death and arresting several of its members.
"We condemn the summoning and arrest of some of our members and demand to stop them immediately," said the Ramallah-based Fatah party, which was founded by Arafat and is now headed by Palestinian president Mahmud Abbas.
Arafat died in Paris on November 11, 2004 at 75 after falling sick a month earlier. Doctors were unable to specify the cause of death and no post-mortem was carried out at the time.
Palestinian society has long given currency to the rumour that he was murdered, and following the findings of Swiss scientists which "moderately" supported the notion Arafat was poisoned, Palestinian officials openly accused Israel of "assassinating" him.
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Israel flatly denies killing Arafat.
Its statement on Sunday, Fatah also called on Hamas "to end the division and achieve national unity" and appealed for it to reverse its ban on the commemoration of Arafat, "the symbol of Palestine and all liberation movements in the world".
But Hamas spokesman Sami Abu Zuhri blamed Fatah for thwarting efforts of his Islamist movement to hold a joint ceremony.
Fatah "insisted it should be only a Fatah ceremony" and decided to not attend a joint meeting that would determine the factional representatives of a memorial ceremony, he wrote on his Facebook page.
Tensions between the two sides have been high since 2006, when Hamas trounced Abbas' long-dominant Fatah in Palestinian legislative elections, and boiled over into vicious street battles between gunmen from both sides later that year.
The ferocity of the violence shocked Palestinians, splitting them into rival camps and the occupied territories into two separate entities, with Hamas unchallenged in Gaza and Abbas's power base limited to the West Bank.