(KUNA) -- Four Palestinian activists were killed Friday when Israeli warplanes raided areas in northern Gaza Strip, said eyewitnesses. In Sheikh Zayed city, an Israeli jet fighter fired two missiles at a moving car killing two activists of the Al-Aqusa Brigades, military wing for the Fatah movement. The attack also resulted in the injury of several civilians, according to the eyewitnesses.In another Israeli air raid on Sakkah area east of Jabaliya refugee camp, two activists from Al-Nasser Salahuddin Brigades, military for the Popular resistance committees, were killed. According to Israeli sources, the army forces began an offensive against Palestinian activists in order to protect its citizens from so called terrorist attacks.