At least five people have been shot dead at a memorial rally for the Palestinian leader Yasser Arafat in the Gaza Strip.
Dozens more were injured after violence broke out between Hamas, who won control of Gaza in June, and Fatah, the secular party of President Mahmoud Abbas.
It is unclear how the violence began. Hamas security officials said they fired at protesters who threw stones at security compounds.
But witnesses said the first shots were fired after crowds accused Hamas security forces of being a proxy for Iran.
Since Arafat’s death in 2004, Palestinian politics has been marked by divisions, the most violent between Fatah and Hamas.
A sea of yellow flags filled the huge square in Gaza City, as as many as 250,000 people gathered to pay their respects.
Hamas have banned opposition rallies but to have prevented people from marking the anniversary of Arafat’s death would have been extremely unpopular.