Supporters of the Palestinian Fatah party have held a massive rally to mark the third anniversary of former leader Yasser Arafat's death.
The square in central Gaza City where the rally took place was a sea of yellow - the colour of Fatah.
It was the largest rally to be held by the party since it was ousted from power in Gaza by rival faction Hamas in June.
Tensions reportedly rose when the crowd began chants accusing Hamas security forces of being a proxy for Shia Muslim-ruled Iran.
The security forces reportedly opened fire on the crowd, causing people to flee.
Hamas officials said they had fired toward protesters who threw stones at security compounds.
Several people were killed and more than 100 were wounded in the clashes.