Scores of fighters on Thursday fought a column of tanks and armoured vehicles as Israeli troops took up positions in and around the teeming Jabalya camp, a resistance stronghold, in an operation the army said was aimed at stopping rocket fire into Israel.
Among the five killed was also a 24-year-old member of the Palestinian resistance movement Hamas.
Helicopter gunships fired missiles into the camp of 100,000 inhabitants as Israeli forces sealed it off in Israel's biggest incursion in the northern Gaza Strip in months.
Shot in chest
Munir al-Deqqes was shot in the chest while playing with friends outside his grandfather's house, witnesses said. "How can anyone blame children playing in the street?" said the boy's uncle. "Munir was a victim of blind Israeli retaliation."
At least 35 people, including fighters and civilians, were wounded by Israeli fire, medics said.
An Israeli military source said soldiers had shot only at fighters. It was the latest chapter in Israel's military response after human bombers killed 16 people in southern Israel last week.
"We urge the ... civilised world to stop these crimes by Israeli occupation forces..."
foreign minister, Palestinian Authority
The raid marked a widening of Israel's incursion that began on Wednesday when forces swept in and seized control following a barrage of makeshift rocket strikes in southern Israel.
"We urge the ... civilised world to stop these crimes by Israeli occupation forces and call on the United States to shoulder its responsibilities towards the peace process," Palestinian Foreign Minister Nabil Shaath said in a statement.
Meanwhile, in another incident a 15-year-old Palestinian was killed when he was run over over by an Israeli army jeep during a brief incursion into a refugee camp near Rama Allah in the West Bank, sources on both sides said.