Fighting between armed Palestinian groups in the Gaza Strip have been occurring on and off for about nine months, and have claimed the lives of 163 people between October and May. Fifty-one people were killed in internecine violence in the month of May alone. During this period, armed activists abducted activists from opposing groups, uninvolved civilians, and foreign journalists, and held them hostage.
In light of the events in the Gaza Strip over the past year, B'Tselem is deeply concerned for the welfare of the civilian population and calls on the armed Palestinian groups to respect the rules of international humanitarian law set forth in Article 3 common to the four Geneva Conventions, which apply in non-international conflicts, and apply, regardless of the circumstances, to all persons taking part in the hostilities. This article specifies four kinds of acts that are forbidden in respect of persons who are not involved in the hostilities, including combatants who have been wounded or have laid down their weapons: "(a) violence to life and person, in particular murder of all kinds, mutilation, cruel treatment and torture; (b) taking of hostages; (c) outrages upon person dignity, in particular, humiliating and degrading treatment; (d) the passing of sentences and the carrying our of executions without previous judgment pronounced by a regularly constituted court…" Breach of these prohibitions constitutes a war crime, for which the violators are held personally responsible.
http://www.btselem.org/english/Special/20070613_Inter_Palestinian_violence.asp