JERUSALEM (AFP) - Israel vowed to strike back at Hamas on Sunday after renewed rocket fire from the movement's Gaza stronghold two weeks after the end of a bloody war in the battered Palestinian territory. "We've said that if there is rocket fire against the south of the country, there will be a severe and disproportionate Israeli response," Prime Minister Ehud Olmert said at the weekly cabinet meeting. "We will act according to new rules that will guarantee that we are not dragged into an incessant tit-for-tat war that will not allow normal life in the south of the country," Olmert said. "The situation... in recent days has increased in a manner that does not allow Israel not to retaliate in order to make sure that our position... is understood by those involved in the fire. "The response will come at the time, the place and the manner that we choose." Defence Minister Ehud Barak said that "Hamas was given a very serious blow and if necessary it will be given another blow." And Benjamin Ben-Eliezer, infrastructure minister and a member of Israel's powerful security cabinet, said the Hamas had to pay for each rocket fired. "We have set a price for each rocket fired and now Hamas has to pay," he told army radio. The officials spoke after four rockets were fired from Gaza into Israel within the space of a few hours on Sunday. But Hamas slammed the Israeli threats as a "campaign stunt" before the election. "This is an attempt... to destroy the Egyptian efforts to improve the calm," Taher Al-Nunu said in a statement in Gaza. Next week's election is expected to bring the Israeli right-wing back into power, according to opinion polls. Olmert, forced to step down in September amid corruption probes, is not standing and his centrist Kadima party " now led by Foreign Minister Tzipi Livni " is trailing behind the right-wing Likud of former premier Benjamin Netanyahu. The Hamas spokesman did not say whether they were behind the rocket fire, but called on "all groups to respect the national decision concerning the ground situation in Gaza." The Al-Aqsa Martyrs Brigades, a group loosely linked to President Mahmud Abbas's Fatah movement, claimed responsibility for firing two projectiles on Sunday.