Complex sentence: One of the remaining militants reported that there is a warrant for the arrest of one of their number, Sean Anderson, but the others are free to go, but they are refusing to do so unless they are all allowed to go freely.
Split into simpler sentences: One of the remaining militants reported that there is a warrant for the arrest of one of their own, Sean Anderson, but that the others are free to go. However, they refused to do so unless they are all allowed to go freely.