Raid Abu Sayf of al-Aqsa Martyrs Brigades and Wayl Salih of the resistance movement Hamas both sustained fatal injuries when an Israeli helicopter opened fire on Friday at the Jabalya refugee camp, the focus of a massive operation in the area which has left 127 Palestinians dead.
Amin Masud, another al-Aqsa Martyrs Brigades activist, was also killed in the pre-dawn strike.
Israel previously announced it was scaling back its military operation Days of Penitence, which it said was designed to put a halt to missile attacks on southern Israel from Gaza, nearly three weeks after its launch.
But its attack on the Jabalya camp on Friday morning wounded four Palestinians in addition to the three fatalities.
The Israeli military operation is continuing, contrary to what the Israeli media has been reporting, according to Wail al-Dahduh, Aljazeera's correspondent in Gaza.
Israeli military helicopters, unmanned planes and tanks and troops are still on alert.
Al-Dahduh said Israeli surveillance planes remain visible. Each plane is equipped with two rockets. When it observes a Palestinian target, it launches what Palestinians call "deadly arrows".
Israeli army makes no distinction
between fighters and civilians
The result is either deaths or severe injuries. Victims are not limited to fighters but include Palestinian civilians as well, he said.
In fact, most victims of Israeli military strikes happen to be civilians, children, women and elderly people among them, al-Dahduh said.
Friday's deaths in Jabalya camp mean a total of 4491 people have been killed since the outbreak of the intifada in September 2000. Of them 3463 are Palestinians and 954 Israelis.