Israeli aircraft fired a barrage of missiles at buildings used by Palestinian terrorists in the Gaza Strip, as the offensive entered its fifth day. The army also fired artillery shells for the first time, signaling that Israel is prepared to hit back even harder. The assault showed no sign of letting up, despite a pledge by Hamas and Islamic Jihad to halt rocket attacks on Israeli towns. Israel says it's setting out new rules of deterrence now that it has pulled out of Gaza, and it urged Palestinian leader Mahmoud Abbas, also known as Abu Mazen, to take action. "If Abu Mazen wants to continue to survive and to continue to rule his people, he first has to rule the Hamas and the Islamic Jihad,” said Israeli spokesman Ra’anan Gissin. “He has to dismantle the terrorist organizations."