From the site Carol linked to:

"13 June, 06: Qassam rocket-fire at the civilian population

Over the past weeks, Palestinian groups in the Gaza Strip have intensified the Qassam rocket-fire at Israeli population centers.

The Palestinian organizations responsible for the rocket-fire state openly that one of their aims is to kill Israeli civilians. Deliberate attacks on civilians are both immoral and illegal. The willful killing of civilians is classified as a grave breach in the Fourth Geneva Convention and as a war crime that is unjustifiable under any circumstances. Furthermore, Qassam rockets are themselves illegal, even when aimed at military objects, because the rockets are so imprecise, and thus endanger civilians situated in the area in which the rockets are fired or where they land. Therefore, the persons involved in firing the rockets violate the requirements of distinction and proportionality, which are fundamental principles of international humanitarian law.

To aggravate matters, many of the rockets are fired from, or near, areas in which civilians live. International humanitarian law prohibits attacks from inside or near the homes of civilians, and from using civilians as human shields. IHL's objective is to reduce to a minimum injury to civilians during an anticipated military response by the other side. The Palestinian organizations that carry out the attacks against Israel from within or near a populated area breach this rule; in doing so, the organizations show their indifference to the loss of Israeli and Palestinian lives."