Fatah officials say their Hamas rivals have arrested the group’s senior leaders in the Gaza Strip as part of a continuing weeklong crackdown.

The Fatah officials say Hamas forces arrested around 15 of Fatah leaders in the roundup early Friday. They spoke on condition of anonymity because they fear for their safety in Hamas-controlled Gaza.

The Hamas crackdown against Fatah began a week ago after a mysterious Gaza explosion that killed five Hamas gunmen and a child. Fatah says more than 200 of its men have been seized, while Hamas has refused to give a number.

In response, Fatah forces in the West Bank have seized dozens of Hamas members.

Hamas spokesman Sami Abu Zuhri says his movement’s new Gaza arrests were a response to Fatah’s West Bank crackdown.