More than 20 Palestinians in the Gaza Strip were wounded on Friday in violence sparked when Hamas forces arrested some 20 members and supporters of rival Fatah in one of Hamas's largest sweeps since it took over the territory.
Fatah and Hamas spokespeople said at least four senior Fatah members were taken into custody in the northern town of Beit Hanoun.
"Four Fatah leaders were arrested not because of who they are, but for violating public security," said Saber Khalifa, a spokesman for Hamas's Executive Force, without elaborating.
He added the men were being interrogated.
Beit Hanoun residents said Hamas forces fired into the air to disperse relatives of the detainees, mainly women, who protested against the arrests near an Executive Force post.
Television also showed footage of Hamas men later raiding several weddings near the area. Residents threw stones at them while the forces fired back and in the air.
More than 20 people were injured in the fighting, including one who suffered a gunshot wound, witnesses said.
A Fatah source said Hamas forces also detained at least 15 supporters of the group in Khan Younis, located in south Gaza. There was no immediate Hamas comment on those arrests.
Hamas took over the Gaza Strip in June following weeks of battles against Fatah militants. The Islamist group won a parliamentary vote last year and was part of a unity government with Fatah before talks broke down prior to the violence.
Hamas forces on Thursday detained a hospital doctor affiliated with Fatah for several hours a day after he was fired from his managerial post. His arrest had prompted protests by his fellow medical workers.
Abbas has refused to recognise Hamas's former government, which now control Gaza. Hamas has also accused Fatah forces of arresting scores of its members in the West Bank, where the president still holds power.