Fatah said about 15 representatives of Palestinian President Mahmoud Abbas had been arrested in Hamas-controlled Gaza.
Hamas spokesman Sami Abu Zuhri told Al-Jazeera the arrests were a response to Fatah's failure to release the Hamas members that had been detained in the West Bank several days earlier.
"These people will stay under arrest until the West Bank authorities release Mohamed Ghazal, a member of the political leadership, and his comrades," Zuhri said.
Abbas had ordered his Fatah-dominated security services in the West Bank to release all pro-Hamas activists, according to the official Palestinian WAFA news agency.
Fatah seized dozens of Hamas members after Hamas detained more than 200 Fatah men following a Gaza bomb attack that killed five Hamas members and a child.
