In the northern West Bank town of Nablus, six Palestinians were wounded, two of them seriously, in clashes between Hamas and the rival Fatah faction of Mahmoud Abbas, the Palestinian president, medics and witnesses said.
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.
Gaza has recently been the scene of increasingly heavy fighting between Fatah and Hamas.
Tensions have been high in Gaza after Abbas called for early elections on Saturday.
Hamas, which trounced the once dominant Fatah in January polls, said it would boycott a new poll.