Clashes between Fatah and Hamas fighters were also reported in the northerth West Bank city of Nablus.
Al Jazeera's correspondent said that a group of Hamas fighters had come under fire while preparing for a ceremony to mark the movement's foundation.
One Palestinian civilian was seriously injured in the attack, the correspondent said.
Gaza has recently been the scene of increasingly heavy fighting between Fatah and Hamas.
Tensions have been high in Gaza after Mahmoud Abbas, the Palestinian president, called for early elections on Saturday.
Hamas, which trounced the once dominant Fatah in January polls, said it would boycott a new poll.