Celebrations to mark the 43rd anniversary of the founding of the Palestinian Fatah movement turned into deadly clashes on Monday.
Palestinian medical sources say five people were killed in fighting between Hamas and Fatah supporters in the Gaza Strip.
The fighting began when Fatah activists rallied in the southern town of Khan Younis, despite a ban by Gaza's Hamas rulers.
Medical workers say in addition to the dead, about 40 people were wounded in exchanges of gunfire in Khan Younis and Gaza City. At least one youth, one Hamas security officer, and one Fatah supporter were among the five dead Palestinians.
Also Monday, Fatah said Hamas forces briefly detained one of Fatah's top officials in Gaza, Ibrahim Abu al-Naja and shaved off his mustache in an effort to humiliate him. The Associated Press reports that Hamas denied involvement in the detention.
In another development, Palestinian President Mahmoud Abbas said in a speech that he is ready to open a "new page" in relations between Hamas and his Fatah party.
But, he repeated a call for Hamas to relinquish control of Gaza before reconciliation talks begin.
Speaking in Ramallah, Mr. Abbas called for dialogue between rival Palestinian factions and said military conflict should not be part of the Palestinian vocabulary. He also revived a proposal for early elections to help resolve the internal Palestinian conflict.
Tensions between Hamas and Fatah have been high since the militant group won parliamentary elections in January 2006, routing the incumbent Fatah administration. The tensions erupted into deadly fighting that peaked with Hamas's takeover of Gaza in June.
Hamas spokesman, Fawzi Barhoum responded to Mr. Abbas' speech by rejecting his conditions for talks.
Some information for this report was provided by AFP and AP.