The Palestinian militant group Hamas used force to prevent supporters of the rival Fatah faction from holding Friday prayers outdoors in the Gaza Strip, wounding about 20 people.
Witnesses say Hamas security forces with rifles and clubs beat worshippers who had gathered in defiance of a Hamas ban on such gatherings. Clashes took place across Gaza.
Hamas last week banned public prayers in the Gaza Strip after Fatah used a service to protest Hamas' rule in the impoverished territory.
Groups affiliated with the Fatah-led Palestine Liberation Organization have called for a general strike on Sunday in the Gaza Strip to protest the Hamas violence.
During last week's Friday prayers, Hamas forces fired shots into the air and beat and arrested Fatah supporters.
Hamas alleges Fatah has used the outdoor services to incite violence. Fatah accuses Hamas of driving its supporters out of Gaza's mosques.
Palestinian President Mahmoud Abbas, who leads Fatah, appealed to worshippers to avoid any confrontation with Hamas forces, which, he said, will not hesitate to use what he called the most gruesome and repressive measures against civilians.
Hamas seized control of the Gaza Strip in June after factional fighting with Fatah that killed more than 100 people. President Abbas dismissed the Hamas-led Palestinian government and named another administration, based in the West Bank.
Some information for this report was provided by AFP, AP and Reuters.