Six people have been killed during clashes at a Fatah demonstration in Gaza commemorating the death of Yasser Arafat.
At least 50 more were wounded when shots were fired in the crowd of almost 500,000 Fatah supporters.
Hamas security forces had been monitoring the memorial event for the late Palestinian leader and Fatah founder.
The event, to mark the third anniversary of the death of Mr Arafat, is the biggest rally organised by the Fatah party since last year.
Fatah's forces were driven from Gaza in a bloody takeover in June.
The city centre was filled with a sea of the yellow flags of the party, which is currently led by president Mahmoud Abbas.
The Islamist Hamas movement, that has controlled Gaza since the takeover, broke up several smaller Fatah demonstrations yesterday and arrested a number of Fatah supporters.
Palestinians across the occupied territories had been paying tribute to the iconic leader who died on 11 November 2004 and remains a symbol of Palestinian unity.
