Hamas has rounded up scores of Fatah activists in the Gaza Strip following a rally that drew more than 200,000 supporters and ended in gunfire that killed seven people.
The rally, marking the third anniversary of the death of former Palestinian leader Yasser Arafat, was the biggest held by President Mahmoud Abbas's Fatah group in Gaza since Hamas Islamists seized the territory by force in June.
Fatah supporters taking part in an anti-Hamas rally in the West Bank city of Ramallah. Photgraph REUTERS/Loay Abu Haykel
A spokesman of the Hamas-led Executive Force said it had detained about 50 Fatah members since the rally.
"They are the ones who planned and organised the rally yesterday and are suspected of being responsible for the chaos that took place," he said.
A Fatah official said Hamas security forces arrested 400 Fatah members and that dozens more were ordered to report to police stations for questioning.
The rare Fatah rally broke up in chaos after gunfire rang out. Seven people were killed and 80 wounded, medical officials said.
Fatah officials accused Hamas forces of opening fire at the crowd, but Hamas said its men had come under attack from Fatah gunmen and returned fire.
Mr Abbas, preparing for a US-hosted conference with Israel later this month on Palestinian statehood, has ruled out new dialogue with Hamas until the group relinquishes control of the Gaza Strip.