Hamas forces arrested about 20 Fatah members late Friday in the northern Gaza Strip for "violating the law," Hamas said, sparking a protest from relatives of those arrested. Some 150 woman and children took to the streets, storming Hamas headquarters in the town of Beit Hanoun, demanding their relatives be freed. Witnesses said the protesters were beaten with sticks. Ten were evacuated to a local clinic for treatment, medical officials said. The arrests mark the first time since Hamas's bloody takeover of the Gaza Strip that it acknowledged it had arrested Fatah members because of their affiliation. In the past, Hamas had claimed to only arrest individuals for specific crimes. Earlier Friday, thousands of Hamas demonstrators took to the streets of Gaza to protest the death of one if its people in the West bank, whom Hamas said was tortured by Fatah forces loyal to Palestinian Authority Chairman Mahmoud Abbas.