The Al-Aqsa Martyrs Brigades, an armed offshoot of the ruling Fatah faction, said it had fired two missiles at dawn into southern Israel in response to the killing of two Palestinians on Saturday, one of the most violent days in Gaza since Israel pulled its troops out of the territory in September.

While the new attacks did not cause any casualties, they looked set to prompt more retaliation from Israel after its defence minister, Shaul Mofaz, pledged to match fire with fire.

Israeli aircraft carried out four raids on Gaza overnight, concentrating on an area from where makeshift rockets had been fired into Israel on Saturday, without causing casualties.

"One of these attacks targeted an office organizing terrorist activities and three others targeted a sector in the north of the region from where Qassam rockets have been fired at Israel," the Israeli army spokeswoman told AFP.