The festival in Nablus marked the 25th anniversary of the founding of Hamas. Ma'an News Agency reported thousands rallied. The New York Times put the number at hundreds of boys and men marching through the ancient city's alleys.
The rally began at the al-Nasr Mosque in the Old City of Nablus, and the secretary-general of Fatah's revolutionary council, Amin Maqboul, Nablus Gov. Jibrin al-Bakri and other Fatah officials joined the assemblage, Ma'an reported.
The head of a coalition of independent leaders, Khalif Assaf, said the festival marked the beginning of the end of national division. Hamas holds power in Gaza.
Waving green Hamas flags, demonstrators chanted: "From Gaza to the West Bank, our unity is honorable, a national reconciliation, Fatah, Hamas and the Popular Front for the Liberation of Palestine," Ma'an reported.
The Times said demonstrators shouted slogans about Palestinian missile attacks on Israel -- "Qassam, repeat it, Tel Aviv, destroy it," and "Qassam, repeat it, hit Haifa this time."