Mofaz ordered the occupation army on Thursday to use all necessary means to deter Palestinian fire, which continued for a second day with several makeshift rockets hitting southern Israel but causing no damage or casualties.
Mofaz's orders followed the worst day of fighting in Gaza since the sides declared a ceasefire in February.
Palestinian fighters in Gaza have fired three rockets into Israel, causing no casualties but putting further strain on the truce.
The Qassam rockets aimed at Israeli communities southeast of the fenced-off Gaza Strip landed in open fields on Thursday, Palestinian officials and the Israeli army said.
Fighters also fired seven mortar shells at Jewish settlements in Gaza, injuring no one.
Aljazeera's correspondent in the southern Gaza city of Khan Yunis, Samir Abu Shammala, said Palestinian resistance fighters fired rockets and mortar shells at Israeli military posts and settlements in several areas in the Gaza Strip for the second consecutive day.
On Wednesday, fighters launched 31 mortars into settlements in the territory after a Hamas member was killed in disputed circumstances.
A Palestinian woman mourns the
death of a Hamas fighter in Gaza
The al-Nasir Salah al-Din Brigades, the military wing of the Popular Resistance Committee (PRC), and the Abu Ali Mustafa Brigades, the military wing of the Popular Front for Liberation of Palestine (PFLP), have claimed responsibility for firing rockets and mortar shells into Israeli settlements in the Gaza Strip.
Izz al-Din al-Qassam, the military wing of Hamas, said it had fired mortar shells and al-Qassam rockets at Israeli settlements in the Gaza Strip, wounding an Israeli soldier.
Palestinian resistance groups said the attacks were in response to what they called Israel's constant offensive against Palestinians and in reprisal for the deaths of Ahmad Barhum and Ahmad Shahwan in Israeli firing.
Israel responded with a missile strike from an unmanned drone on a mortar squad, killing one fighter.
That drew fresh threats by Hamas to abandon the ceasefire before Israel's planned withdrawal from occupied Gaza in August.
Israeli Prime Minister Ariel Sharon was to consult security chiefs later on Thursday to decide on a further response to the mortar and rocket attacks, Israeli radio stations reported.
Meanwhile, a Palestinian Interior Ministry official on Thursday accused Hamas of sparking a clash in the Gaza Strip on Wednesday that wounded three members of the Palestinian security forces.
Hamas says Israel's constant
attacks need a response
Fighting in Khan Yunis broke out after the
security officers tried to stop a group from firing mortars at a Jewish settlement.
Palestinian Interior Ministry spokesman Tawfiq Abu Khusa told Aljazeera: "There is no doubt Hamas participated in the incident in collaboration with activists from the Abu al-Rish Brigades in Khan Yunis."
"Opening fire at Palestinian police by armed Palestinians is a dangerous act that is unacceptable and unforgivable," Abu Khusa said.
Security officials in the area have identified some of the attackers as Hamas members, he said.
The Palestinian Authority (PA) as well as the Islamic resistance group Hamas on Thursday accused Israel of trying to wreck the truce.
"The Israeli aim now is to sabotage Palestinian President Mahmoud Abbas's upcoming visit to Washington," PA Foreign Ministry official Abdullah Abdullah told Aljazeera.net.
He accused the Israeli army of carrying out "unprovoked missile attacks on Palestinians who initiated no violence against Israeli targets".
Hamas also accused the Israeli government of seeking to trigger violence to appease Jewish settlers opposed to the planned Israeli withdrawal from the Gaza Strip.
Hamas spokesman, Sami Abu Zuhri, said Hamas remained committed to the calm but added that the movement would hit back if attacked.
Aljazeera.net's Khalid Amayreh in the West Bank contributed to this report.